Yes, the Windows 95 RegClean utility can be run on Windows XP. Whether it should be done or not is a matter between you and your PC.
In my case, I am used to doing regular reinstalls of Windows - or, at least I was before I started using XP.
I was a regular user of Win9x from 1996 to 2001; at work, I switched over to NT/2000 in early 2000 and at home ran it occasionally until August 2001 when I finally switched to the XP Release Candidate.
During that time, I became very familiar with the guts of the desktop operating systems since I seemed to need to do a reinstall every 30-60 days. After my switch to XP, I rapidly discovered that I was losing my touch - in fact, the only significant reinstall I had was when I upgraded to the release version of XP (I had to - the 180-day demo was on the verge of expiring).
In any case, I did discover that I was accumulating a large amount of garbage in my registry due to all of the ActiveX components I worked with. Unfortunately, I have not run across a utility designed for XP that works the way I want: automatic scanning and removal of all missing components, coupled with archiving to an easily re-merged REG file. In other words, nothing that works like RegClean did.
After playing with it a bit, I discovered that RegClean appears to run quite successfully on XP if told to run in Win98 compatibility mode - so that's how I use it every few days, and it seems to work quite nicely. I have not yet run into any difficulties with it and don't expect to.