Windows 2000. Likes to freeze and/or crash with random blue screen errors.

I reformatted and reinstalled Win2k two days ago, got the modem and video card running yesterday. And since yesterday, my computer has been very problematic. It likes to freeze up whenever it feels like. It froze up earlier right before the log in screen was displayed, while I was waiting for a webpage to load, and when I clicked a button on a flash game. It seems to be random. Also the blue screen likes to pop up and piss me off. So far I've received:

- Ntoskrnl.exe - IRQL_NOT_EQUAL_OR_LESS
- NTFS_FILE_SYSTEM

- Win32k.sys - KMODE_EXCEPTION_NOT_HANDLED

-Ntfs.sys - NTFS_FILE_SYSTEM

Also without listing filenames:

- An attempt was made to write to Read-Only Memory.
- UNEXPECTED_KERNEL_MODE_TRAP

System Specs:

- WIndows 2000 Professional SP4 Build 2165
- AMD Sempron 2800+
- 768Mb Ram (One 512Mb PC3200 in DIMM Slot 1 and a 256Mb PC2100 in DIMM Slot 2, compatible)
- Jaton GeForce4 Ti 4200 128Mb 4x AGP
- Intel 536EP Modem
- Sound Blaster Live!
- 19.8Gb Quantum Fireball Hard Drive

Everything on my computer is brand new, except the hard drive and video card, which are both a couple years old.

Any suggestions?