Do you have one of these products ?
If yes, which one ?
"If you cleared the CMOS by temporarily moving the CMOS jumper to the clear position and then back while the computer was unplugged..."
"unplugged wafer batter let set one minute put it back in "
or if you removed the Cmos battery from the mboard then re-installed it the RIGHT way so the + is showing on it when it's installed, you will get a message from the bios "Cmos Checksum Error" or similar. You must go into the bios Setup and set at least the date and time to get rid of that message while booting, OR, if you are able to get your operating system to load after you get that message, if you change the time and date in the operating system, that will change the time and date in the bios, and you will no longer get that message while booting. .
NOTE that if the Cmos battery is not installed in the mboard, or if it is installed in the mboard but it's installed backwards, or if it is installed properly but it's too weak or dead (typically they last up to 5 years or so), the bios will behave as if the battery was not installed, and you will get the message every time you boot the computer, at the very least whenever you have shut down the operating system and then boot the computer.
"have switched the 3 pin jumper on motherboard by power unit, "
That's useless information when we don't know by what you've told us what the 3 pin jumper or more likely 3 pin header is for, or what mboard you have.
"beeps 2 times then beep stays on"
The beep or beep pattern error codes generated by a bios version vary depending on which brand the bios software is, and on when the bios version was released.
e.g. the brand may be Award, Phoenix, AMI, etc., or a brand name system bios version based on one of those
Do you see Award, Phoenix, or AMI (American Megatrends) on the screen while booting ?
There is often some beep or beep pattern error code that indicates
- a ram problem or no ram installed.
If you have ram installed, disconnect the AC power to the computer and make sure it's all the way down in it's slot(s) and it's installed in the right direction. The bump or bumps in the bottom of the slots must line up with the notch or notches in the bottom edge of the ram module(s).. (If any of the ram modules were installed backwards, both the ram module and the ram slot circuits of the slot the backwards module was installed in are fried instantly when you attempt to boot the computer and neither one can ever be used again, You may or may not be able to get the mboard to work in that situation - you must clean up the black carbon deposits and any plastic that was melted and is bridging contacts in the damaged ram slot, then the mboard MAY work fine when you install undamaged ram in undamaged ram slots).
- no video adapter connected, or a problem with a video adapter - e.g. a poor connection - if you're using a video card that installs in a slot, make sure it's all the way down in it's slot. ALWAYS remove the AC power to the computer whenever you plug in or unplug a card in a slot, or check the seating of a card, or the ram !
If you have both onboard video and a video card installed in a slot, try removing the video card and connecting your monitor to the onboard video's port.
There must be a 3 or 4 wire fan connector connected to the 3 or 4 pin CPU fan header.
If the keyboard is USB connected, the bios Setup must have Legacy USB or USB Keyboard or similar enabled, otherwise the USB keyboard can't get into the bios Setup.
Older bioses may have that disabled by default - newer bioses usually have that enabled by default.
You can always get into the bios with a PS/2 connected keyboard.
If you're using a PS/2 connected keyboard,
- it must be plugged into the PS/2 port all the way BEFORE you attempt to boot the computer. PS/2 devices are NOT "hot pluggable" - plugging it in or unpluuging after booting the computer while the computer is running can damage the PS/2 device's circuits or the PS/2 port's circuits or both.
- it usually MUST be plugged into the RIGHT PS/2 port (usually it's colored purple) - it usually will NOT work in the PS/2 port for the mouse (usually colored green.
- if you are using a USB to PS/2 gender adapter to adapt a keyboard with a USB connector on the end of it's cord to PS/2 port use, the keyboard will NOT work unless it's a "combo" keyboard - wired up and meant to be used with either a USB or PS/2 connection.
" a green light comes on by the HDD connector on motherboard; "
Most modern mboards have an led that lights up when the power supply has been connected to the mboard and the power supply is receiving live AC power, whether the computer is running or not. Usually it can only be one possible color.
That led is there to remind you that the ATX family mboard is always powered in some places, even when the computer is not running, and you are supposed to unplug the computer or otherwise switch off the AC power to the computer whenever you're going to be fiddling with any wiring or component connected to the mboard or the drives.
Some mboards also have one or more other leds, that light up only when the computer is running that indicate something else, and that/those led(s) may have more than one possible color, one of the colors indicating an error condition.
E.g. some have an led that indicates whether the ram is working properly or not.