Thanks for all the suggestions.  I had the idea that there was a problem due to three things:  a new piece of software reported .dll's that were supposedly in the C:\documents and settings\Admin\Local Settings\Temp folder that I did not find when I looked using Explorer - so I thought it might be stealthed .dll's.  I ran Ice Sword and did a log and reboot but that program failed to start up after that due to an initialization error, so I was starting to worry.  I found nothing with Process Explorer, but a well-stealthed root kit might not show with that.  I then ran Rootkit Revealer and found two keys with embedded nulls and a key that Revealer could not access.  I booted with a PE disk and looked at the \Temp folder again and saw a .dll file, but with a different name than the ones reported before.  I  tried using the Regdelnull (Sysinternals) file on the registry and used the remote registry editor to look at the result.  Well, the inaccessible key turned out to be a SCSI driver key, with an owner name that was a long string of numbers.  I could not delete the key, but I was able to edit the key's values and I renamed the .sys file that it pointed to (no SCSI connections on my system, so I was not worried).  The owner string probably refers to a system ID for SCSI devices, but I didn't need to take the chance that it was dangerous, so I nuked it.  Turns out the file was harmless according to Virustotal's scan.  The keys with embedded nulls are apparently legitimate??!!!  If you see a Rootkit Revealer report that shows:
HKEY_LOCAL_MACHINE\SECURITY\Policy\Secrets\SAC
HKEY_LOCAL_MACHINE\SECURITY\Policy\Secrets\SAI
as keys with embedded nulls, they are probably not a problem (although a rootkit that used those keys would be a real problem, because Regdelnulls doesn't touch it).  After a few more checks, I think that it was a false alarm, But I was beginning to think that I had an unknown rootkit, especially when I had crash problems with Sysinternals' Autoruns when I referred listed items to Process Explorer.  Anyway, thanks again, especially for your suggestion jgpaiva.

XP for me!!  I bought my first new computer in six years in 2006 just to be sure that I would not have to be saddled with Vista.  I had been happily using Win98 but the threat of built-in DRM and the enormous overhead that it requires spurred me into action.  The video drivers for video cards have become gigantic - one set of drivers for an nVidia board was as large as the NT 4.0 o/s.  It is no wonder that the Vista systems are slow with that kind of overhead.  The Vista components are now written in "modules".  There are 6 (I think) video modules, of which 4 are concerned with security.  The size of the o/s is another problem.  There is no way that the o/s code can be grown by a factor of eight without a performance hit.  As for the security of the o/s, it is a bit different from XP, so it will take a few months for the hackers to catch up.  From my recent reading, all that it means is that rootkits will be written in User mode rather than Kernel mode to circumvent the User Account Management feature.  All this wonderfulness is costing us money.  When there is a huge coding overhead for Vista drivers, hardware manufacturers will add that to the price of new hardware.  In addition, because of the performance hits, we will have to buy better hardware to enjoy the same performance.  Add this to the generally user-unfriendly approach of Microsoft - limited installs of the software you have actually paid good money for - activation on only one machine, ever, meaning that if you upgrade your hardware, your o/s may no longer work - and you can count me as a no for Vista, and a vote for XP only because there is not a better choice without having to learn Linux.  Every time I think about Vista, I come back to Linux.  I may go there yet.