A new computer! Windows 7! Forget that unless you have handfuls of money to spend.
Ever since my very first ex-government IBM 8088 purchased for $20.00 I've always built up my own machines. I always like it when new technology comes along because it means that suddenly heaps of the just rendered obsolete tech can be picked up for pocket change.
I've only just built up a machine with DDR RAM because SDRAM has been just so darn cheap to buy up until now, but it's getting harder to find which means that I've finally gone up a notch to DDR.
I use Pentium 4 based motherboards because....
(6) they're very cheap to buy.
(7) any more whizz-flash architecture than that and you're just fooling yourself unless you're doing major software development or graphics work.
8. most will take 1.5 - 2.0 Gb of RAM which is all I want or need.
The machine I'm typing this on used to be a 1.6Ghz Compaq Presario, but it's now got a P4 3.0Ghz processor which I picked up for virtually nuffing and fitted to the original motherboard. It's running 1.5 Gb SDRAM and an old but goody Gainward gaming video card. I added around three extra cooling fans to the case as well which has cleared up all tendencies for this machine to cook itself, - which it used to do all the time in its standard condition
I'm also running Mandriva Linux as an operating system because Ubuntu doesn't like my broadband modem and won't work with it. I have a Windows XP install on this machine still, but I haven't used it in aaaaaages.
My spare machine is built into an old server case because it has a power supply that could run a small town and a cooling system to die for. The whole thing including the original dual processor motherboard cost me $50.00.
I almost wept when I had to finally replace the old motherboard, but the sad truth was that a P4 processor based motherboard was just plain faster and less troublesome. 2.0 Gb DDR RAM and an 'obsolete' AGP Gigabyte video card with a Gig of RAM on board put the cost up by around $80.00 along with various other bits and pieces. Once I track down a bigger hard drive this will be going from being the spare computer to being my main machine.
I use Puppy Linux on a boot disk to get inside computers that have gone bad. Just about compulsory equipment to have if you're running Windows. And for heaven's sake you must always run decent anti-malware software!
I use AVG with Windows and find it very good. Malwarebytes is good too.
Old XP install discs aren't hard to find. I've still got the one that came with my Compaq and I was given another one recently when I bought an old laptop. If you need an OEM code to activate it go buy an old case from a computer recyclers it will have a code stuck on it somewhere and it's waaaaaay cheaper than buying a new Windows disc (just make sure it's for the right version of Windows though).
I wouldn't go buying Windows 7 just yet, - wait a few years. It will be cheaper then and it should be common knowledge whether it's a lemon or not.