Is this the machine on which you reinstalled the operating system on a new hard drive..?? Your description of "the first few times I started it, I would get a blank black screen" makes it appear like the machine is new. If so, take it back and get a replacement..
If this isn't a new machine, please describe which SP Service Pack you are using (RIGHT click on "My Computer", choose "Properties". On the "General" tab, you should see the operating system and service pack version.)..and tell us more about what you've done recently which could have caused the issue.
Have you tried following the procedures in the links below to stop conflicts at start up and clean things up a little? If not, please do:
For Windows XP, ignore the first couple of sentences about checking "resources" in the link below but follow the rest of the procedures including the "Services" links at the bottom.
How To Shut Down Unnecessary Start Up Programs
How To Clean Unwanted Files From The Hard Drive
After following all the procedures above, run Error Checking/Chkdsk and Defrag to optimize the hard drive:
How To Run 'Error Checking/Chkdsk' On Win2000/XP
Hope this helps and let us know how it goes.
Grif
I'm using Windows XP. I started my computer, and it went to the Windows Loading screen where the bar goes across from left to right. However, when that screen would go off, normally Windows would come up, the first few times I started it, I would get a blank black screen. I'd wait and nothing would happen. I maually restarted the PC, and it came up with a screen saying that Windows failed to start correctly(or something like that). It gave me options to either start Windows normally, start Windows with the last known working settings, or start in Safe Mode. I tried starting normally, that didn't work. Then, I tried with my last working settings, that didn't work, either. Then, I tried in Safe Mode, and it started. I ran Check Disk, and found no errors. I really didn't know what else to do, so I tried to just restart. That time it worked and Windows came up like normal.
Anyone, know what the problem might be?
If you need more info, just ask.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic