I've used GoToMeeting for this, and I think you can get a subscription for $50/year.
Wouldn't that only be for access to a single computer? Matt mentioned "computers," so I think he's looking for more than one. Besides, that requires software to be installed on the computer being remotely accessed in advance, which isn't very handy for remote support.
No, with the subscription you can "host" a meeting. Anyone can join a hosted meeting for free, and once joined they can hand over control of their computer to another attendee (or the host).
The software is downloaded and installed automatically when the user attempts to join the meeting via the web site. A small little application is downloaded and installed. If my uncle can manage it, *anyone* can.
J
Edit: I was wrong, it's $50/month, but it's priced by the organizer (meeting host), so this would work perfectly. The annual price is $468/year -- don't know if this is too expensive, but the service works beautifully.