More info....
Trying to boot the computer as-is results in some fan turning on, but never any signal to the monitor, no POST, nothing. Press the power button and it immediately powers off (don't have to hold it in).
Took both DIMMs of RAM out....same as above (did not beep or seem to "care" that it has no RAM).
Inserted one of the DIMMs...got a splash screen for something which said "System Boot Failure" at the bottom, frantically pounded the keyboard, must've hit the boot options key, selected the hard drive, and the computer did not boot any farther, lost the signal to the monitor, had to hold in the power button to shut it off.
Inserted the other DIMM of RAM...got another splash screen but no boot error, pressed F8, chose Start Windows Normally, then lost the signal to the monitor, had to hold in the power button to shut off.
Tried each DIMM in the other spot...got the same results as before: no splash screen, no POST, no way to get into setup or boot options. Actually, one time the monitor got a signal for about 3 seconds (light went blue) but never got an image.
Tomorrow I plan to take it to work, remove all the components and blow the whole thing out (it's packed with dust). If I could just get it to boot off a disc I could roll back the update with System Restore (I have all the Windows DaRT discs at work). It's just too large and dusty to deal with at home tonight. Any other suggestions would be appreciated...