What do you use your PC for?
If you just surf the net then Linux will be fine, in fact it'll be a lot safer than using XP.
OpenOffice is a fair substitute for Microsoft Office providing, like most of us, you don't use 80% of Office's whizz bang features.
I've used Gimp for photo editing but it's nowhere near as feature rich as Adobe Photoshop or Corel.
Download the CD and have a play around.
Windows and Linux are quite quite different.
http://www.ubuntu.com/getubuntu/download
I believe you can boot off the CD and run the OS without actually having to install anything.