Sp!ke
Administrator
Interestingly my PC has been hanging on shut down and I'm pretty sure it's since SP3 was installed.
It does shut down eventually but takes a while.
Turn off system restore and then click apply and then turn it back on again (best to use less than 12% of your disk though).
Your machine is trying to take a restore point at shut down and is struggling to write with all the fragments on the drive.
Ideally you should turn off system restore, then defrag and then turn it back on again. I only assign about 3Gb for the restore files, not 12% as is default which or toidays sized drives is massive overkill.