Vista - Black Screen, loads after 10 minutes

Hi, I'm new here (nice to meet you all). I am a basic computer user that knows how to download, install, and fix basic problems. However, this is seemingly too advanced for me, unfortunately.

I have a Gateway LX6810, preconfigured from Best Buy with Vista Home Premium x64, 8 gb of DDR2 Ram, an Intel Core 2 Quad processor (at 2.33 ghz), and a Nvidia GeForce 120 video card.

My exact problem is as follows: My computer has been running fine since I got it about 2 weeks ago. It loaded fast, opened programs quickly, and was able to play Fallout 3 on max specs (other than resolution, as I have that set to my tv's 1280x720 ratio) with no stutter.

Now, as of three hours ago, I get the black screen everytime I start, right after the green Microsoft load bar. It lasts about ten minutes, then when the "Welcome" screen with the circular cursor comes up, that lasts another minute. I haven't really downloaded anything in the past few day, other than a small video file (which I watched and had no troubles with), so I don't think its that. Also now it takes Firefox about 30-40 seconds to load up instead of two or three. Normal folders still open very quickly. I'm half afraid to try a game right now.

I had noticed something funky when, about 5 hours ago, I went to open a rar file and it took about 2 mins to open. Keep in mind that I had opened that rar file a day or two ago without a hitch. About half an hour later, I shut off my PC. Realizing I wanted to look something else up on the internet, I turned it back on, to discover my current problem.

I did the startup repair thing, even restored my Vista to about 13 hours ago. I did the memory scan thing and then tried safe mode (as I didn't realize my Vista would eventually load if I just let it go).

Startup repair and the memory scan found nothing, the restore didn't change anything (Black Screen still is there anyways), and safe mode loaded all the drivers and stuff very quickly, then sat for about 7 to 8 minutes before finally loading.

I wasn't quite sure what I was looking for, so I didn't really find anything out pertaining to the possible cause of my situation.

Well, thanks in advance if you read this entire post (sorry for the length), and double thanks if you can offer a possible solution.

Click on the start orb.
Click on search and type in msconfig
when msconfig loads look for autostart programs, it is possible that one of these may be causing problems. Turn them all off and slowly turn them on one at a time after every boot.
Also look at your processes to ensure nothing nasty is hiding.

this may sound like killing a fly with a sledgehammer, but if your computer is only 2 weeks old and you havent really loaded too many programs AND you can back up any important data, i would consider restoring to factory conditions (assuming you have a restore cd)

Ah, I forgot to mention that due to the fact that it is preconfigured from Best Buy/Gateway, Vista is already installed and there was no disc included. Thanks for your suggestions so far. I'm going to try the startup-program thing.