My PC wont restart properly anymore

[lokodezine]

Hello,
My computer when ever it has to be restarted because I restart it or because I just installed a program that requires it to be restarted it always shuts down then begins to restart and it goes all the way to the loading screen (the black screen with Windows XP and the blue loading bar moving) and then restarts again.

After the second time it starts up and I am able to login but before it gets there it comes up with a black screen asking me since the PC did not shutdown properly would I like to start the PC in Safe Mode, Last Known Good Configuration Point or Start Windows Normally. I usually choose normally.
Then since it did not start properly the Internet never works (I have wireless internet). So then I have to shut the pc down and then turn it back on. It’s quite a pain and I wish it would just restart correctly.

My questions are:

1) What could be causing this? Could it be something wrong with an outdated driver? Something internally wrong with one of my drivers? Could it be a lose wire?
- Because I had this problem before and then I reformatted my hard drive and it still had the problem. I got Ad-Aware SE, Trend Micro Internet Security, and Webroot Spy Sweeper as well running. I ran all three of those programs in Safe Mode and it still did not restart properly… What could be the problem?

2) Also when installing a program and it says “The computer must be restarted to finish installation” will the program be fully installed if my PC restarts twice and messes up on the first attempt and second attempt I am prompted on which state I would like my PC to startup in.

Thanks
* If you need any more info please let me know