Richard writes:

<<"! Explorer "this program has performed an illegal operation and will be
shut down." The details are "explorer caused an invalid page fault in
module sirapi.dll.">>

I've never heard of that file.  Locate it on your computer, rename it, and
see what happens.

Chances are, it's a remnant of one of the viruses you think has been
removed (how did you remove them?) or some other nasty. Possibly, if the
file opens at startup, as many of these things do, it won't allow you to
move or rename it. If so, try opening in Safe Mode and rename from there.
Otherwise from a dos boot floppy.

Reinstalling Windows won't help if there are still nasty things on the
computer. They are often well hidden, and some are very difficult to
remove.  You may need to save what you can and reformat to do a complete
job of eliminating all these nasty things.

Run Msconfig and untick everything except Explorer and Systray. See if that
eliminates the problem.

Don Penlington
 From the Beach at Surfers Paradise in sunny Queensland.
Computer tutorials and other things at my website:
http://users.tpg.com.au/deepend/index1.html

             PCSOFT maintains many useful files for download
                     visit our download web page at:
                  http://freepctech.com/downloads.shtml