The secret to upgrading follows..
Rule #1.
Purchase a newer faster hard drive than is currently in the machine, a 7200RPM is the minimum...
Rule #2.
review the listing of devices in the device manager and write it all down, you'll need to record the network card, sound card, graphics card, ...
Rule #3.
Visit the vendors site and determine what Windows 7 drivers are available... IF none are listed, that's not the end, the original maker of the chipset may have them.. Visit Intel.com and go to drivers and let it's analyzer take a peak and see if it recognizes the chipset and more...
The two single most drivers you want to have on a usb stick are the CHIPSET INF drivers and and the NETWORK CARD Drivers, with these you'll at least be able to download others...
You'll also want to download a windows executable BIOS upgrade file. I won't talk about the hard way...
Given that you can find some drivers for Windows, I'd go for it...
Rule#4 did you make a set of Windows 7 Installation DVD from your machine.. Nows a good time...
Install or have a friend install the new hard drive....and use your Windows 7 DVD to install a fresh copy of Windows 7 onto the new hard disk.. (THE OLD HARD DRIVE is you get out of JAIL free card) if all goes to %$^$^, simply reinstall the old one.
Assuming Window 7 installed, install the CHIPSET drivers, then the LAN card, Graphics, card,
If you have a newer Intel Chipset, a chipset that support Rapid restore, you should have also download the RAID drivers, and set the ATA settings to.....AHCI
Intel Board also like the AMT drivers,, and integrated graphicss.....
After installing Windows 7, disable the search service, disable the AERO interface, and search for a listing of services that can be disabled in windows 7..
If you've made it this far, I can assure you that Windows 7 will run better that Vista, and in most case faster than XP....
I've tweaked a few hundred installations of all of them, for work and pleasure...