|As I'm running Windows ME and 98SE, I couldn't possibly recommend that you down-grade to Windows XP. :-)|
Why would you want to leave the safe haven of Windows 9x, for which no one has been writing viruses or malware for a VERY long time, for the murky waters of XP with all of its security problems? No rootkit virus ever destroyed a Win9x system, for the simple reason that they can't run on Win9x.
Some high-end WinME systems have hardware which is technically capable of running the early releases of WinXP. I haven't done it myself, but I have come across cases of Windows 2000 and early Windows XP versions running on WinME hardware. Particularly in dual-boot scenarios. (Why does everyone want to dual-boot these days?)
If you're going to try it, don't go mad and wipe your hard disk. Buy a new disk, and install XP onto that, keeping your existing disk as Primary Slave in case you change your mind - or the rootkit rot gets you!
Bear in mind that the term "bloatware" was invented with WinXP in mind. Watch your system's speed slump, as it struggles with an O/S that doubled in size compared to Win9x. Technically, you can probably do it, but it may play merry hell with your patience!