System hang at startup

I began to notice my computer hanging at start-up a few months ago. It would do all of its normal booting sequences as normal, it would even start that progress bar when Windows begins to load... but after (what I presume to be the computer finishing loading Windows) nothing happens. Black screen. My TV screen and my monitor go into standby mode. After holding the power button to turn the computer off, I would restart it and it would start normally, no complications.

After a month, it would require -two- of these reboots to get it to run. -Today-, when I started the computer, before the computer did -anything-, I got consecutive, rapid beeping AND it took 3 shutdowns to get the computer to respond.

I'm not a computer tech, but I wanted to venture a bad boot sector? Any information (relating to the computer >>) I'd be happy to give if it helps.

As this post is located in the Windows Vista section, I'm sure a guess can be made as to the operating system. :D

OH! I should mention that this happened -before- too. Eventually my system's performance degraded to where I had to completely reinstall Windows. I -really- don't want to do that again, that's why I'm here.

Perhaps it could be a Windows update that's being a pain? It seemed to happen when I downloaded an update from Microsoft... so perhaps that could be a possible problem?

ANY and ALL help is completely appreciated!
-Brandon