If it is only the hard drive & you have your old windows cd you can just get a new drive and install whatever version of windows you want.

Or is the whole computer old and you are looking for a new one?

Most Windows vista,7,and probably 8 too - can be stripped down to look/act more like XP.

But there is also free Linux OS /aka distros to be had

In fact I wiped my last years Compaq w/win 7 laptop and installed Linux Mint KDE- love it and much faster without all the MS & HP bloatware.

finds most drivers automatically and all I had to do was put in our wifi password to connect it to our wireless modem.
It is not hard to figure out like in the past - many distros are very much like windows as far as using & looks.
(many years ago linux was a mystery, but now it is becoming more main stream and beginner friendly)

info-
http://neurotalk.psychcentral.com/post945833-7.html