Major help plz! pc going crazy

ive just installed/built a pc for my m8
its

amd xp 2000
256 RAM
geforce 4 ti
20 gig hd

etc
a lot of the parts were from my old pc so i know there all working.

The computer has been running fine until we got the internet for our uni house. His computer is set to host a 1 mbit line accross a network of four pcs. Using a USB modem suplied by Telewest

Seemingly randomly his computer will start chocking, loading really slow, choppy sound, games running really jumpy. Mouse lagging

When i run taskmanager the cpu usasge is flucating between 4-60% even when system idle is on 99, and all other programs are doing nothing.

i cant seem to see any aplications running in there that could cause it

ive run spy bot, adaware, trendmicros free virus online scanner (which initialy reported a trojan, but couldnt clean it, and doesnt detect it anymore)

but cant seem to find out whats wrong
if i un-plug the internet from his pc it seems to be ok

im pretty handy with a computer yet i cant find anything wrong.

Could it be that the USB connection is just not up too much?
or a trojan?
ive run Hijack this but cant see anything suspicious
the only time when i have problems is when its on the internet.
But it doesnt do it everytime


Sorry for such a long post, but im really stuck as to what to do
any help or advice would be greatfulyl appreciated

 

h

forgot to note
its started restarting itself every now and again =/

it will just randomly reboot

 

try running McAfee avert stinger. if you have a worm or virus it will eliminate it for you or allow you antivirus software to remove it...

 

thx for the quick response

but unfortunatley it didnt find any of the 33 trojans =/

so still stuck as to whats causing this
its doing it now, mouse lagging a few seconds behind
and the cpu usage flucating loads

 

You might take a look at your registry with Regsupreme it works fast and it's a 30 day trial.
What AV application are you running BTW?

 

Ive used trend-micros online scanner
nortan antivirus

and AVG

none found any viruses

ran the MS blast fix, didnt find anything

but the welcher virus was found, and removed

maybe something do with that


although ive had a few people say it could be the USB modem
So ill try swapping to PCI

fingers crossed that will sort it out

thx for help though guys, ill keep informed =p
i will fix it somehow!

 

just when i think ive cracked it the problem returns.

if i unplug the internet it seems to sort itself out. But problem still persists now util i shut down SVCHOST

now im not sure of the full workings of SVCHOST, but i know if i close it down the problem goes away. But that means my network and internet stop working..

so baffled as to what to do next
i thought maybe a virus or a trojan is nestled away in there, but ive run so many virus and trojan scanners to no avail.


the computer only has 256 megs of ram, could that cause a problem?
theres between 2-4 computers on the network at any one time, but it slows down seemingly randomly, making games impossible (laggy sound, laggy graphics) or broswing the net hard, due to laggy mouse

all the other computers on the network run fine

and i have the microsoft firewall enabled
anyone has some advice =)

 

hope this helps

sounds to a similiar problem i had

What i did was get hijackthis and ran it it found all the software running in the background you may wont to make a note to see if you have some weird java app running in the background, or some spy-ware/ad ware.

The key is hijack this

caution though if u dont know something in hijack this dont delete till your positive it isnt important to your os

good luck
d

 

Since SVCHOST has a lot to do with your network, this article might help. You might want to follow the links on the page and let Symantec do a virus scan -- hey, couldn't hurt