The stop message means that a memory access violation has occurred (the 0XC0000005 part of the message), see
I suggest that you run the memory tests in the Dell diagnostics.
As far as your BIOS is concerned, for the Dimension 2300, the last BIOS update was A02, in September 2002, so unless you got your PC before that date you probably already have that. You can check by entering the BIOS when you start your PC, immediately before Windows starts loading, press F2 repeatedly to Enter Setup. You should see the version there.
Other possibilities are driver conflicts: have you updated any drivers prior to this beginning, or added/replaced any hardware components?
XPS630i Quad Q6600 @ 2.4 GHz BIOS 1.0.13 FSB 1066MHzRAM: 3 GB PC6400 DDR2 SDRAM 800MHzHDD: 2x WD25 00AAJS-75VWA 250GB SATA non RAIDDVD: Liteon DH-20A1S and HL-DT-ST DVD +-RW GSA-H73NVideo: GeForce 8800 GT 512 MBAudio: Audigy 2, Altec Lansing ADA995 5.1 speakersMonitor: Dell 1800FP
XP pro SP3 IE8 WMP 11