Permissions Failure

I was one of the many people who wanted to upgrade to Mac OS X 10.6.
And so I did, two days ago.
I installed Snow Leopard, installed my classic apps, like Photoshop, Firefox, etc. (most of them not being "Snow Leopard-ready yet) and it was all OK. Then I learned about the 64-bit kernel thing, and I downloaded this app: 32- or 64-bit Kernel Startup Mode Selector for Mac.
Couldn't use it, cause I found out my Late 2007 iMac didn't support booting in 64-bit kernel mode.
So I deleted it. Then I installed some plug-ins. DivX 7, and Flip4Mac.
Somewhere at that point my Mac started to behave REALLY abnormally.
Occasional hiccups, little freezes, and EVENTUALLY it locks up for good.
I then reboot, and the loading screen comes up with a loading bar.
I'd wait for like 15 minutes, and I got to the blue screen before you get to your desktop. But I never got to the desktop really...
I reinstalled Snow Leopard, and after the second or third boot, the same thing would happen. Tried Leopard. Even Tiger. Nothing.
Checked the RAMs. Nothing.
I then noticed I couldn't "Repair Disk Permissions". The option's disabled on the Disk Utility when I boot from the Snow Leopard Installation DVD.
Now I'm stuck with my freakin' Boot Camp partition, typing this through Windows 7...

What could it be guys?? I'm getting really freaked out!!!
It's been two days now without OS X
PLEASE. PLEASE!!! SOMEONE, HELP ME!!

Eeek.
Ok, strange that you can't get into disk utility to repair, that shouldn't happen.
Anyway.
I would run an FSCK check then to verify the disk and file system. This should allow you to fix any problems within the OS itself.
I can only think the cause may be some kind of conflict between 32 and 64 bit apps, but that's speculation.
If you need to know about FSCK, just use the search engine. There are a fair few posts telling you how (quite a few by me).