my 2000 to XP upgrade worked ok, but performance was much better with a fresh install. 2000 and XP don't degenerate over time as much as 98 does, but I'd expect a performance hit with 98 to XP.
However, XP is not 100% compatible with older stuff, so I can dual-boot. 98 on a small FAT32 partition and XP on the rest in NTFS. It's the best of both worlds.
