malware?

i have a gateway system with a 633mhz chip
win xp office
40g h/d
when i boot up i get a window that pops up and says
this system is shutting down.
save work,etc.
initiated by NT AUTHORITY\SYSTEM
windows must now restart because the remote call (rpc) service terminated unexpedly.
before i started getting this message i was having a malware prob with a browser hihjack. which i believe i have removed.
any help would be greatly appreciated.

 

sorry
it restarts 40seconds after this window pops up.
and keeps doing this

 

ok i was bale to check the system
there are no service packs installed and i was wrong its xp professional
i also believe its a bootleg
ive tried to install the service packs and they wont load because of that.
also i didnt see msblast listed when i hit ctrl/alt/delete
the system wont stay running long enough to run anything.
from power on to the shutdown is maybe 5 min max
3 of those 5 are used in the boot process.
once my background loads ive got a max of maybe 3 min
before it starts shutting down and restarting
i get the feeling im forked here
thanks for the quick response
any other ideas?

 

anybody have any ideas?

 

ok here i go
after getting the items you suggested i turned the prob comp on
and noticed that on startup that my avg kept popping up a window stating that it couldnt start.
so went in to start up and disabled it as well as zonealarm seeing as how i wasnt connected to the net.
this increased my " on " time to roughly 11 mins.
no i do not get the rpc box the comp now just restarts without any warning.
ok now to the items i downloaded.
the ms blaster told me that ms03-26 needed to be installed
so i searched the net and found windowsxp-kb823980-x86-ENU.exe that had the needed fix.
now i get a window that tells me it could not verify the integrity of file update.inf. and to make sure the cryptographic service is running.
as for the macafee avert and sasser tools the comp wont stay running long enough to complete them.
my main concern for trying to fix this thing is that its a new western dig. h/d
and i had a lot of pictures on it that i hadnt gotton on to disc.
with the extended time i gained i have managed to get the pics on disc.
i would now not have a prob with reformatting the h/d.
i actually tried this before i posted here and got a window that told me it couldnt be done. sorry i forgot to write the reason down for this.
is it poss to reformatt with the disc provided with the h/d?
or does any 1 think that i can fix this prob?
thanks

 

update
while looking for a file my wife needed on the prob comp
i ran across the following - winsockxpfix.exe
so i ran it. after which the comp stayed on without restarting for about
a hr and a half. during that time i ran a 2005 version of stinger that found nothing. i then shut it down to post here and get the other dloads.
i am getting ready to try running the new stinger and sasser dloads to see what happens.
will post results later
if any 1 has any other suggestions let me know
thanks

 

ok the stinger and sasser both ran all the way through
without finding any probs.
the prob comp seems to be staying on now
however when i went to the device manager the list wouldnt
come up.