If you have the reinstall CD for the operating system, you could just boot to the CD. Then, once it is loaded you will get a screen asking you which partition you would like it reinstalled on. Myself, I usually just delete the recovery partition if I have a reinstall disk, but that's just me. On that same screen where you pick where you want to install Windows XP, you can also delete other partitions if you would like. When doing a fresh install, I always just delete all the partitions, then you will only have one option, which says "Unpartitioned Space" (something like that) and you just select that since it is your only option. Deleting the other partions, you just use the arrow keys, select the one you want to delete, hit 'D', then it will prompt you 'Are you sure' etc, and then you have to hit 'L' on the keyboard.
Then, after this step you are given options to format NTFS, NTFS(quick), and possibly FAT. Obviously choose NTFS, (or quick) and you will be on your way installing Windows XP, fresh install. You most likely will have to load the drivers for a lot of the devices, if you your enternet or wifi drivers you can try and use Windows Update to find those drivers.
Hope this helps, maybe see what someone else recommends too...a lot more smarter people around here then me...
Oh and instead of Firefox, you should try out Chrome