If she's running 32 bit Vista, you can use Sandboxie free version.
http://www.sandboxie.com/Install has an option to put a button on the QuickLaunch bar to
run the default browser sandboxed. Browsing is the most likely
place to pick up viruses. Although you can run email and other
programs sandboxed if you want to.
What I like about Sandboxie, is that it doesn't slow your whole
system down just to try to filter everything.
It uses a device driver for the HD. Any program running sandboxed
that thinks it's writing to the HD is really writing inside the sandbox
folder. The free version does all you need. I paid the $25 just because
I like the approach at it wasn't exorbitant. Might be up to $30 or so
now.
Plus for power users you can set the Sandboxie service to run manually
to allow starting and stopping when needed instead of it running all
the time in the background like virus shields do.
I use the free virus and adware scanners occasionally just to make
sure nothing got through.
