Hanging problems after update to Vista SP1

I just updated to Windows Vista SP1, and I'm having constant problems. I run it on an Acer Extensa that hadn't given me ANY troubles originally.

1) Internet Explorer, both IE7 and IE8 (I upgraded, thinking it would save me--no dice), froze on startup and display the standard "Internet Explorer has stopped working" message, giving me only the option to close the program. Firefox 3.0.19 (I know, out of date) works just fine, and I'm using that to surf for now.

2) Yahoo! Messenger 9. ...something... starts fine, but once the small ads in the box, which I think use Internet Explorer to display, tries to load, it locks up and shows the same "has stopped working" message that IE shows. The Yahoo! Messenger 10 Setup installer also fails when it has to display webpages while waiting. Using Yahoo! Messenger for Web in Firefox works fine.

3) The Data Execution Prevention activated twice (once on shutting Firefox, and once after Internet Explorer 7 had to be closed after freezing). When I click the icon in the tray to get more information, it says "Microsoft Help and Support has stopped working", only letting me close the program.

4) Trying to System Restore to right before SP1 was installed says that the System Restore failed after rebooting the machine. It hung at the "initializing" phase on shutdown.

I don't have a recovery disc or a way to burn one, nor a recovery partition. I do however have a full backup of the C drive obtained via the Seagate external hard drive's own Seagate Manager.

I have attempted to run Internet Explorer without any add-ons without any changes, and did a global reset, also without success.

Can anyone please help me here? I'm at the end of my rope! :cry