Computer Restarts on Install/Uninstall of IE8

I'm a web developer and I only use IE for testing purposes. Today I tried to update my IE8 to a newer version (to match a client's version), and I fear that I have totally screwed things up.

Some basics: I'm running XP Home Edition SP3. Running Avast anti virus, SuperAntiSpyware, frequent checks with malwarebytes. I'm quite certain that I'm not infected with anything (I've been checking).

My first mistake was downloading and trying to install IE8 (it was already installed). When I tried to install, my computer restarted.

I then went to Control Panel and tried to uninstall. The computer restarted.

Back to Control Panel, clicked on "Add/Remove Windows Components", selecting Internet Explorer only. That appeared to work, but nothing happened. If I try opening IE, nothing happens at all.

I went to the Microsoft site and found their "Microsoft Fix-it" utility. That also appears to work, but nothing really happens. If I try to install or uninstall my computer restarts.

With every restart, I get the dialog box saying the system has recovered from a serious error, etc. Here's the details from that message:
Error signature:
BCCode : c2 BCP1 : 00000040 BCP2 : 00000000 BCP3 : 80000000
BCP4 : 00000000 OSVer : 5_1_2600 SP : 3_0 Product : 768_1

To add insult to injury, I did try to log into my Microsoft account. Even after resetting my password, they tell me my login is incorrect. Sigh. I give up on Microsoft.

I wish I could just do without IE, but I have to use it for testing.

Thank you in advance for any advice you can offer!

Michele