|"Does a higher RPM (Revolutions Per Minute) make my computer run faster like having more RAM? If I bought a 7200rpm over a 5400rpm, will there be much of a difference when actually using the computer." |
Adding more ram doesn't make Windows run faster unless the amount you already have installed isn't adequate for the programs you use.
E.g. for XP 256mb is just barely enough for Windows to run at the speed it should, if you're not using integrated video. Many people get by fine with 512mb for most programs. Only demanding programs most people don't use, or high end games, might need more ram.
Ultimate Memory Guide
How Much Memory Do You Need? etc.
The difference between a drive that runs at 5400 rpm in comparison to one that runs at 7200 rpm is mostly the average seek time is proportionately faster on the faster drive (1.33 X in theory), but it's only a difference of milliseconds (thousandths of a second) at best.
The size of the buffer cache on the drive, and the maximum data burst speed the drive can achieve, is more important - e.g. up to 133mb/sec for an IDE drive, 150mb/sec for a SATA drive, or 300 mb/sec for a SATA-II drive.
If the buffer cache size and the max burst speed is the same, you will be hard pressed to notice much difference.
Freeing up space on your too full partition Windows boots from, usually C, definately makes a noticable difference in Windows performance.
Using a video card in a slot rather than integrated video allows your ram to use it's maximum bandwidth - sharing the ram with the video often halves it - and that makes a noticable difference, even with the same amount of ram, especially when your system is being more heavily taxed.
However - your mboard (see the specs below) has no PCI-E X16 slot for a PCI-E video card - it has just two PCI slots, and a PCI-E X1 slot.
You would need a recent chipset PCI video card, or a PCI-E X1 video card if they exist, for the video to be better than the onboard video.
Also, your power supply has only a 230 watt capacity (see the specs below). If you think you may add a PCI video card, check the specs of the particular card on the manufacturer's web site to see what minimum required power supply capacity is, and possibly the minumum amperage it must supply - you may need to get a better power supply as well.
I found the specs for a Dimension 3100 in Australia that has a 3ghz Pentium 4 cpu, Windows XP Media Center Edition 2005, a 160gb hard drive, and 512mb of DDR2-533 ram, but the configurations probably vary.
Make sure you back up your system, and make the Rescue Disk set you're supposed to make, with a program already put there by Dell in your Programs list somewhere, while Windows is still working so you can re-install your original Dell software including Windows if you need to.
If you have Windows XP Media Center Edition 2005, you will need the 2 disk OEM MCE set to load Windows MCE otherwise.
Technical Support for Dimension 3100/E310
System Configuration - enter your service tag to find your exact configuration.
Service manual, HTML (PDF also available)
Specs, for the series:
Those appear to be identical to those found on the USA Dell site.
As OtheHill has already surmised, those specs confirm you can install any size of current hard drive.
If I were you I would install one internally - inside the case - rather than bothering with an external one at all, unless you have a specific reason you want it to be portable.