plagued by BSOD

hi all,

i'm having tons of trouble with my new computer and after fiddling for weeks, i haven't found a solution.
My specs are:

Microsoft XP (SP2)
AMD 64 X2 Dual core 4600+
1 Gig ram
Geforce 6600 512

i'm getting pretty random BSOD's at least once per day, sometimes multiple times per hour. It seems that i only get them when i'm running a resource hogging internet application, such as a firewall, firefox, bittorent, etc.

Here are some of the stop error messages i'm getting before i hit the restart button:

KERNEL_STACK_INPAGE_ERROR <----most frequent stop error
STOP: 0X00000077 (0XC0000185, 0XC0000185, 0X00000000, 0X00****)

DRIVER_IRQL_NOT_LESS_OR_EQUAL
STOP: 0X000000D1 (0X71A5DF52, 0X0000002, 0X0000008, 0X71A5DF52)

KERNEL_DATA_INPAGE_ERROR
*** STOP: 0X0000007A (0XC07BAF88, 0XC0000185, 0XF75F1000, 0X255958C0)
*** MountMgr.sys - Address F75F1000 base at F75EC000, DateStamp 41107b05

For some reason, i never get a dump file after the restart has completed? I've gone into "startup and recovery" under advanced settings and set it for kernel memory dump in %SystemRoot%\MEMORY.DMP . nothing.

also the event viewer doesn't seem to help much. I've ran the memtest86 through 2 passes although i plan to have another go at the memtest and run in through 7 passes.

Any suggestions?

regards,

sam