if youve got a decently fast pc, and can backup your files fine, get XP. you
wont want to go back.
OEM version of XP is fine and a fair bit cheaper, you wont get nearly as good (if any) phone-up-and-chat tech support from MS though. aviod getting "upgrade" windows, installing from scratch is always a lot better.
oh yeah, whats involved:
- backup all your files onto something, like burn onto CD, a second hard disk.
- double check the backups

- download or otherwise acquire XP-version drivers for all your hardware.
- back them up, together with the other files you forgot about in steps 1 & 2

- put XP cdrom into cdrom drive
- restart the computer, go into bios and change "boot order"/"boot sequance" so it is your cdrom first and hard disk second, save & exit bios (there might actually be a time during win98's boot when you can press a key and select where to boot from, cant remember)
- windows XP setup will start
- follow the instructions.
during the instructions you'll need to format your hard disk, which will delete all the files on it. format it NTFS, like XP will reccomend. towards the end of the install it will start talking about finding new hardware, where you'll install your hardware drivers.