After a recent attack by the trojan Spyware Protect 2009, my PC
lost the System Restore function.  The trojan, which bombarded
my system with numerous and frequent popups claiming virus
infestation, was cleaned up but still suffers from aftershock.

A mysterious aftereffect is background audio that
comes on at random times.  The content is non-offensive and
sounds like commercial announcements from an internet broadcast
site.  Removing the internet cable or locking down the firewall
eliminates the intrusion, but that's not the desired solution.
How can I detect where this is coming from?

The System Restore function was originally tried in hopes of
eliminating the trojan, but would not work.  Now I can't even
create a restore point.  The System Restore window displays and
allows me to go through the motions including naming the restore
point, but clicking OK results in the message "Unable to create
restore point, reboot the system and try again".  Rebooting
doesn't help.  It was verified that System Restore and Task
Manager services are active and there is more than adequate
hard drive space available.

Any suggestions short of a Windows re-installation would be
appreciated.