System Unknown prob

[ashfame]

I use win xp sp2 with all updates on a P4 based machine with 256mb ddr ram.
i was just using my comp. & suddenly it hangs (mouse & keyboard) & it shows an error "a usb device has exceeded its power limit" although on usb i only hav 1 printer which was even turned off.
one thing to note is that when it hangs only keyboard & mouse didn't work, the processes behing goes on as usual like antivirus updated itself & shows an message.
i pressed the power button, it begans to shutdown & at the last moment bios beeps continously & system turned off.
Next when i power it on, bios beeps 6-7 times, comp started to boot but the monitor remains off (i.e in the orange light rather than green).
i can't even boot my comp.
wht could be the prob?
pl help, its damn urgent for me!!

[Kratos]

It is important to note how many times bios beeps? Look in your motherboard manual to see the meaning of the number of beeps.

Look here for more info:

http://www.pcguide.com/ts/x/sys/beep/index.htm

[ashfame]

i uses intel d845gvsr mobo. can't find beep codes meaning!
edit:
Number of Beeps Description
1 Refresh failure
2 Parity cannot be reset
3 First 64 K memory failure
4 Timer not operational
5 Processor failure (Reserved; not used)
6 8042 GateA20 cannot be toggled (memory failure or not present)
7 Exception interrupt error
8 Display memory R/W error
9 (Reserved; not used)
10 CMOS Shutdown register test error
11 Invalid BIOS (such as, POST module not found)

[ashfame]

i got rid of this prob by cleaning ram stick but now it shows an error "a usb device has exceeded its power limit" although on usb i only hav 1 printer which was even turned off. & the keyboard & mouse don't work although processes on the screen go as usual.
pl help guys.