A good registry cleaner should alert you the entries that correspond
to missing executeables. Norton System Check (as part of the old
Norton Utilities) is one that I've used for years on Win 98 and Win
ME. It's quite good. The freeware RegSeeker is also useful. But
something like Microsoft's RegClean is "too mild" ... only correcting
more minor problems (from what I have seen).
Insofar as other startup axis items, I like KAV's TrojanFinder (see my
web site). But recognition of illegitimate entries is not automatic.
It requires knowledge. And deletion must be done manually.
For your own personal PCs, it's a good idea to become familiar with
all normal startup axis items and be ready to recognize any intruders.
Art
http://www.epix.net/~artnpeg