|I'm assuming you mean the computer sometimes won't initially boot. |
If it does intially boot but Windows won't load properly sometimes, that's a different problem.
We need info about about the problem computer.
Tell us the make and model of your brand name system, or if you have a generic desktop system, the make and model of the mboard.
The specific model of a brand name system is shown on a label on the outside of the case somewhere, or it can often be determined by going to the brand name's web site.
The model, sometimes the make, of a mboard in a generic desktop system is usually printed on the mboard's surface in obvious larger characters, often between the slots.
The model is often also displayed on a logo (graphical) screen early in the boot, but it's often not as specific as the specific model number.
For Dell computers, they have a Service Tag number - the specific model can be determined by using that on their site, or can often be determined there automatically by you downloading some software. The Service Tag number should be on a label on the outside of the case, probably on the bottom on a laptop, on the back on a desktop, and is often also shown in the bios Setup.
It sounds like this problem computer is a desktop computer.
Common problems that can cause your symptoms....
- the ram has a poor connection in it's slot(s)
A common thing that can happen with ram, even ram that worked fine previously, is the ram has, or has developed, a poor connection in it's slot(s).
This usually happens a long time after the ram was installed, but it can happen with new ram, or after moving the computer case from one place to another, and I've had even new modules that needed to have their contacts cleaned.
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
For a laptop, or netbook, you must remove both its main battery and AC adapter before you do that.
For a brand name computer, see the Owner's or User's manual if you need to - how to remove or replace the ram is usually in that - it may already be in your installed programs. If you can't get into Windows, it may be on a disk that came with the computer, or you can go online and look at it or download it - it's in the downloads for your specific model.
For a generic desktop computer, see the mboard manual if you need to - how to remove or replace the ram is usually in that.
- The power supply is in the process of failing.
Failing power supplies are common and can cause your symptoms.
Check your PS.
They often partially work, fans and hard drives may spin, leds may come on, yet you may get no video and the mboard will not boot all the way.
In the early stages of failiure, the computer may boot fine sometimes, not boot other times.
See response 4 in this:
If it is failing, you can usually replace it with any decent standard sized standard ATX PS with the same capacity or greater.
Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.
Don't buy an el-cheapo PS.
See response 3 in this:
We are seeing this problem frequently lately - someone has installed a video card that requires more than a little more capacity than the existing power supply can provide.
Your power supply must have at least the minumum capacity required to support a system with the graphics card you are using installed, or the max graphics card you might install in the future.
(Onboard video - video built into the mboard - IS NOT A CARD ! )
If that info is not in the ad for the video card, you can go to the video card maker's web site and look up the specs for the model - often under system requirements - the minimum PS wattage, and, more important, the minimum amperage the PS must supply at 12v is stated. If you don't find that, any card with the same video chipset including any letters after the model number has very similar minimum PS requirements. Some power supplies have two or more +12v ratings - in that case, add those ratings to determine the total +12v current capacity.
If you're a gamer...
In most if not all cases, the max capacity rating of the PS is an intermittant rating. It's recommended that you do not load your PS to any more that 80% of that rating if you are going to be using something that puts a constant load on it, such as playing a recent game for hours on end. In that case, you multiply the min capacity stated for the system with the particular video chipset on the card by 1.25 to find the min. capacity of the PS you should get.
- Data cable problems.
It is common to un-intentionally damage IDE data cables, especially while removing them - the 80 wire ones are more likely to be damaged. What usually happens is the cable is ripped at either edge and the wires there are either damaged or severed, often right at a connector or under it's cable clamp there, where it's hard to see - if a wire is severed but it's ends are touching, the connection is intermittant, rather than being reliable.
Another common thing is for the data cable to be separated from the connector contacts a bit after you have removed a cable - there should be no gap between the data cable and the connector - if there is press the cable against the connector to eliminate the gap.
80 wire data cables are also easily damaged at either edge if the cable is sharply creased at a fold in the cable.
Try another data cable if in doubt.
Check your SATA data cables. The connector on each end should "latch" into the socket on the drive and on the mboard, or on the drive controller card - it should not move when you merely brush your hand against it near the socket - if it does, mere vibration can cause a poor connection of it - use another SATA data cable that does "latch", or tape the connector in place.
(There is a slight projection or bump on one side of the outside of the connector that "latches" it into the socket - it's easily broken off or damaged)
The same thing applies for the SATA power connection.
- an optical drive has failed or is failing.
Optical drives (CD and DVD drives) commonly do NOT work properly forever. If an optical drive has failed or is failing, it can cause long delays while intially booting, or possibly failure to boot completely. If you have more than one IDE optical drive on one data cable, or an IDE optical drive on a data cable with a hard drive, a defective optical drive can cause both drives connected to the cable to malfunction.
Disconnect the data cable to all optical drives to see if you still have the booting problem.
Try disconnecting the data cable at the optical drive(s) one at a time to see if you still have the booting problem.
If you have (an) IDE optical drive(s), you may need to change the way the still connected drive is jumpered at the back of the drive if the optical drive was on a data cable with another drive.
Optical drives don't require a data cable connection in order for you to be able to eject or retract the disk tray when you press the button for that on the front of the drive.
As long as the computer is running, there's nothing wrong with the power supply, and the power connector is connected to them, that should always work, except for a brief periods when the conputer's bios while booting, or Windows, is already trying to access a disk in the drive.
"I took out the CMOS battery for a while and that didn't help either."
That never does, regarding the computer's mboard intially booting.
"...went into the BIOS. The 1st boot device was set to the CD rom so I changed it to the hard drive...."
The Boot Order or similar settings in the bios Setup can be set various ways, but there's nothing wrong with a CD drive or similar being listed before a hard drive. If there is no bootable disk detected in an optical drive, the bios will then try booting the next thing in the list in most cases.
E.g. If the Boot Order or similar settings in the bios Setup are set to this, it works for booting from a floppy, bootable optical disk, or a bootable hard drive, without you having to change boot order settings.
- if there is NO floppy in the floppy drive, the bios will try to boot the next thing in the list
- if there is a floppy in the floppy drive and it's bootable, the computer will boot from the floppy in the floppy drive, and the bios will not try to boot from anything listed after it.
- if there is a floppy in the floppy drive but it's NOT bootable, the bios will NOT try to boot from the next thing in the list.
- if there is a disk in the optical drive, if the bios can boot from a bootable disk that's on the optical drive's connection, and if the disk is bootable, the computer will boot from the optical disk, if you press a key while booting when you see "Press any key to boot from CD" or similar while the line is on the screen, and the bios will not try to boot from anything listed after it.
If you do NOT press the key to boot from the optical disk while the line is on the screen, the bios will try to boot from the next thing in the list.
- if there is no disk in the optical drive, or , if there is a disk in the optical drive, if the bios can boot from bootable disk that's on the optical drive's connection, and if the disk is NOT bootable, the bios will try to boot from the next thing in the list.
"if the bios can boot from bootable disk that's on the optical drive's connection"
Many bioses will only boot from a bootable optical disk that's in one optical drive. In that case, if you have more than one optical drive, there is either a list of optical drives in the bios Setup, often near the Boot Order or similar settings, or you can select from more than one optical drive in the Boot Order or similar settings. The optical drive you want to boot a bootable optical disk from must be listed first, save bios settings.
Some older mboards have some SATA headers you can connect an optical or hard drive to that you can boot a bootable hard disk or bootable optical disk in them from, and other SATA headers that you CANNOT boot from a bootable hard drive or bootable optical disk in a drive from. The two types of SATA headers are sometimes different colors, sometimes they're not. Read the mboard or brand name system manual.