windoes 2000 errors

[Mashrur Mia]

Hello,

I have been getting all these STOP errors, lately -

NTFS_FILE_SYSTEM
UNEXPECTED_KERNEL_TRAP
KMODE_EXCEPTION_NOT_HANDLED
DRIVER_IRQL_NOT_LESS_THAN

I did not installed any new hardware or anything.

At last I tried installing windows 2000 from scratch by formatting my
harddrive in low level. Even still I have a stop error, this time it
was

"An attempt was made to write to read-only memory"

any help? should I get new RAMs? I tried different RAM test programs,
they did not get in errors in the RAM...

thanks
Mashrur