Dimension 4700 4-2 beep error/ not loading

My 4700 is not loading when I turn it on. The green lights come on, the fan starts spinning, and it instantly starts beeping. The beeps are very low-pitched, 4, then 2. At that point, everything stops loading. The fan continues to spin, and the lights stay on, but nothing else can be done. The monitor also does not come on.

 

This started a few days ago. My computer froze after getting an odd blue screen warning (I don't remember what it was, but it was NOT a fatal exception). I know it happened after another warning, it MAY have been an active X warning (I don't remember) that said there was an error, would I like to send the error log to Microsoft (the standard warning when anything goes wrong). I turned it off, and when I started it again, I chose to load from the last known good configuration. It worked, and when I logged in, it gave me a warning message about my drivers recently being altered, and if there were any problems, I may have to fix them, but if it's the first time seeing the warning to ignore it. For the record, I've never done anything that could alter the computer in any way.

 

The next time I loaded the comp, the monitor stopped working. If I unplug it from the back of the computer, it instantly starts doing "self test feature check" (a color block going across the screen). When I plug it back in, it instantly goes to standby. Sure enough, I unplug it again, and the self-check starts. I'm wondering if it's a monitor driver issues, because of the previous driver warning. And could it be a virus?

 

Also - the A-D lights on the back of the comp are steady amber on A and B, and steady green on C and D, if that helps.

 

Thanks to anyone who responds!!!

 

Christine