After Vista Startup, Computer Freezes

[EBox]

Hi all-
I'm absolutely desperate at this point and would welcome any thoughts.

I have Windows Vista Home Premium, running on a Dell Inspiron 530, which is only about 1.5 years old.

2 days ago, after I installed a Windows Update, when I rebooted, it logged me into Windows, loaded up all the icons in the system tray, and then froze the screen. Couldn't do anything (move the mouse nor CTRL-ALT-DEL), so had to hard reboot. I did go into safe mode sucessfully, and went to MSCONFIG, basically disabled all Startup programs except for Microsoft ones.

This didn't work. I even tried to install SP2, and this failed to do the job (so I uninstalled that).

I also tried to do the Vista repair by hitting F8 upon boot up, and when I try to do System Repair, it says it didn't detect any errors. I am also unable to do a System Restore from this menu also.

Consequently, I have also run malware checks, MS Security and McAffee scans, nothing has come up.

I'm at my last resort here, and really don't want to have to re-format if I can help it. Can anyone suggest ideas for me to take here?

Thank you-
Ebachenh