Wierd setup problem, get rid of dual boot

My wife's computer is set up to dual-boot Windows 2000
Pro and Win 98; she uses the computer for architectural
drafting with Autocad, and for Internet access. She's
been having some trouble with it recently: after a while
the CPU meter in Norton System Docter goes to 100% CPU
usage, and the computer slows way down. When I check the
Processes list in Task Manager, it shows that a copy of
svchost is the culprit, accounting for at least 99% of
CPU time; however, I don't know how to find out which DLL-
based service this particular instance of svchost is
running. I've scanned for viruses, adware, and spyware
and found nothing. I thought I could simply reinstall
Windows 2000 (choosing to repair an existing
installation). However, when I run the setup program from
the CD, I get an error message after the "Loading
information file" screen (which comes right after the
screen where you have to choose between FAT and NTFS).
The error message says that the installation of an
existing program on the system (it doesn't say what the
program is) is incomplete; clicking on "Details" gives me
a window that says that I should reboot, let the
(unspecified program's) installation finish, and then
restart the Windows setup program. If I do this, however,
no installation program starts when I reboot. Instead, I
get the same old eventual saturation of the CPU. If I
could (somehow) find out what svchost is running that's
causing the problem, could I simply use "Add/Remove
Windows Components" from the Control Panel to remove and
reinstall the offending system component? Is it possible
to do this?

Also,if I ever manage to solve the probelm I just
described, I'd also like to get rid of the dual-boot
option and have Win 2000 only. How do I do that?