Butts

A Windows XP computer without applicable security updates will easily get infected by malware on any sites hosting it. How easily might depend on the age of the disc it was installed from. After installing that OS, you should immediately go to Microsoft's Windows Update site and install all the critical updates.

I remember installing win2000 and being infected with sasser 3 seconds or so after connecting to the network with it. aaaugh.

What is the purpose of this computer anyway? Browsing the internet?

I'd personally just throw some sort of Linux distro on it if you aren't going to do any games.. probably more secure than any amount of security updates Windows receives.