Computer still runs at 100% CPU after reformat and virus/spyware scans

Hey guys I'm in need of help. As of this past Thursday my computer has been causing me a lot of problems. On Sunday I gave up trying to work with the immense lag and ran Spybot S&D. This found a few entries and removed them, I also used the immunize function or whatever it is called. Restarted my computer only to be greeted by the start-up repair. After many times of it looping because of Boot unable to find OS Load, I used the Dell Factory Image Reset tool, basically reformatting my entire hard drive. The problem continued even after I did this, so I ran a virus scan. Two minutes in my computer completely shuts off. I waited 30 mins and turned it back on. This time no sign of lag in my performance of high CPU usage. It was actually down to around 8-10%. Then I installed the 89 windows updates for my computer. While my computer was installing the updates during a restart, the computer completely shut off again. Turned it back on and it ran smoothly saying all updates had been installed. When I woke up the next day the computer had shut down. Turned it on and the lag was back. 100% CPU Usage with task manager using about 45-50, with everything else using at most 10%. I ran Adaware and my computer came up clean. I'm about to run another updated virus scan, but my real question is that I'm beginning to think it is a hardware problem, any ideas? - Also I have not installed any new hardware lately. Thanks for any help you guys may have.
 
Can you give the spec of your pc? Or is it a bought, known model/type?
In task manager, performance tab, what do the 'cpu usage' and 'memory' show on the graphs?
 
I'm running a Dell Inspiron 1521. Running on a AMD Turion 64x2. Memory is 993MB out of 2GB. And CPU is showing 80-100%. And for the past hour anti-virus scan has been sitting at 2% with 1867 files scanned.
 
Ok. I was interested to find if you had 1GB or 2 RAM, but 2GB is ok.
You have Vista (or poss upgrade to 7), so to rule out any O/S problems, without causing any more, I would think it a good idea to run 'chkdsk /f'.
So that's 'Start', in the search box type 'run'. When 'run' appears at the top of the list, right-click on it and choose 'run'.
In the box that appears, type chkdsk /f
(There is a space after chkdsk)
Click 'ok'. In the new box that appears, type Y
Close the box, Restart the pc and leave it. Could take some time, 45-60mins.
(You may know all this, but it can only do good to a faulty O/S).
See what happens after this.
If your antivirus is sitting at 2% for all that time, that's not right. Be interesting to know what you are using.
 
No trouble. It's worth running chkdsk /f now and then, it's sorts out many minor Windows problems.
I was going to ask if you had 2 different anti-virus programs installed and running at the same time, it can have a similar effect to what you had. One detects the other and it slows the system.
I run Windows 7 firewall, and Microsoft security essentials anti-virus, that's all, and have no problems so far.
 
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