HELP ME!!!! SL Freezing at Login Screen

Please help me. I used to be able to hang out all day long, and as far as I can tell my comp meets all the requirements, but I can't seem to even get past the login page. Once I got as far as Verifying Protocals (or whatever) before it froze up on me.

I have unistalled and reinstalled about three times in the last three days, and I even tried using the old version off my backup disc, but that just told me to update. I really want to play/live/whatever.

Sony VAIO
MS Windows XP, Service Pack 2
Intel(R) Pentium(R) M
processor 1.70 GHz
209 MHz, 512 MB RAM

Erm. If you need more info than that, you'll need to tell me how to find it. Yes, I know this is a laptop, so the lags and occasional minor glitches were expected, but I had to completely remove the program due to major crashes, and now I'm completely unable to get on at all. I'm very sad. Help.