Windows 7: Windows 7 crashing post-login screen

Hi there.
So, my computer was working fine 15 hours ago, playing games and loading webpages and all that. I turned it off for the night and when I turned it back on this morning it booted properly, as per usual. So then I logged in, the screen turned black, my cursor appeared and nothing else happened.
I've been trying to fix this problem all day and if I leave it for long enough it does log in properly, but I was wondering if maybe one of the start-up systems isn't working right or whether I just need to do a disc cleanup.

Running Windows 7 Home Premium 32bit, and the average wait time for it to load (when it does load, which is occasional) is about half an hour.
Also running Windows 7 on a Mac, because my school gave it to me for phr33 at the end of their Mac phase.

Go through the steps for Troubleshooting Steps for Windows 7

   Warning

Some of the steps require that you open up your system, so before doing any of the re-seating and connection checking steps, answer these two questions: Are you still under warranty? Does your warranty allow you to open up the machine to check hardware? If you are unsure of the answers to these questions, contact your system manufacturer. WARNING: Some steps in that tutorial involve removing the system case or system panels and can void your warranty!!!

The steps specifically related to the warning are steps 8, 10, and 11.


Let us know if you need help with any of those steps as you proceed.