Yep. No microswitch on the I/O panel. I suspect either the switch on the front panel or the ribbon cable itself is the problem. This is starting to get to the "too hard" limit. I suspect I'll discover that the control-panel cable is not a replaceable component.
Now I've got to buy my daughter a new PC for school and go figure out how to transfer all her stuff off of a hard drive in a dead desktop onto a laptop drive. Jeeze!
OK Thanks folks. The responses and support from y'all ha been great.
The plan is now this:
Order new Dell inspirion laptop for the Grrl - it's about time she had a laptop anyways. Can't really complain too much about the 4600c desktop. It has survivied 2.5 years of college usage and at least ten teardown-pack-transport-setup cycles, more than a desktop should really have to endure.
Order a usb external drive case-only and mount her old drive in it. Plug into laptop port and transfer all her data over to new machine. Now she's fine an can go back to school in working order.
Follow your advice and try Dell parts and see if I can get the 4600c working again - if so, pitch MY older still Dimension 4100 and replace with the the 4600c. That way everybody gets some sort of upgrade and even the usb drive case is still useful since I can reformat the drive from my old machine and use it for extra storage or back-up.
Jbirk - you da man (I assume...)
Time for me to fess up - although I've been using PCs at work since about 1982, they're just tools to me like a power drill or a calculator. I've rarely had to get into the guts of one since the long-ago days when you had to install the processor and memory boards yourself when they were delivered. I have no clue how to get down to the part number level or even how to contact "Dell Parts". Further, despite serious attempts, I still can't figure out how to get that dang cable/button/switch loose from the friggin' front panel of the case.
I'm just learnin' as I go and trying to resist a screwdriver as pry-bar and brute force.