Here's some screen prints of the event logger on recent shutdowns. Not sure if this is what you need.
Also, it seems some of the failed shutdowns don't even show up in the event viewer!
It has had a couple of normal shutdowns tonight, but still persists in either failing to shutdown or taking up to 5 minutes.
I've scanned it again with Housecall, which came out clean. I've defragged and ran disc cleanup, with no avail.
Brand: Hewlett Packard
Processor Brand: AMD
Processor Type: AMD Athlon
Processor Speed: 2.9 GHz
RAM Size: 4 GB
Computer Memory Type: DDR3 SDRAM
Hard Drive Size: 750 GB
Graphics Card Description: ATI Radeon 3000
Graphics RAM Type: DDR3 SDRAM
Graphics Card Ram Size: 1.87 GB
Voltage: 240 volts
Wattage: 90 watts
Operating System: Windows 7 Home Premium 64-bit