there is also the option of linux operating systems, a lot of these will run quite efficiently on less powerfull (or older to some people) hardware,
most linux distro's come with all the drivers and software you need, the version i run has thousands,
there are live cd's to try which will not mess with your hard drive,
if you like one then you can install it to your hard drive and off you go,
linux live cd list,
linuxall it takes is the time to download, an iso burning program and a few blank cd's,
the downside is - its not windows, it may take a while to learn different programs (eg openoffice instead of microsoft office)
worth a look ?,
oh - most are free (including all the software)