I have a reasonably new HP laptop running Windows 7. For convenience I will explain my problem in bulletpoints:
-When I sign in into my account, the laptop becomes slow and according to the task manager my CPU usage is 100%. Although no programs are running. I tried to identify what uses up that much CPU but I am not that ace with Windows 7.

-My guess is it has something to do with USB ports. One time during shutdown the laptop gave me a cute little blue screen saying something about an error with usb.sys or something.

-Also one time I started up the laptop but it was just a black screen and constant beeping. That carried on untill I disconnected all of the USB devices.

-I tried to uninstall all USB drivers but it didn't help.

- There is also a problem with my sound device. Constant crackling noise which dissapears after 10 or 20 minutes of using my laptop. But I think it might be a seperate issue.

-Now here is the strange bit. After 10 or 20 minutes of use, my laptop calms down and CPU usage drops to between 10 and 20%. I have no idea what to make of it. Maybe it has something to do with the sound device. I tried disabling it in Device manager but the high CPU usage persisted.

Usually when I have a problem I just google for the solution, but this time I am perplexed. There are 10 billion different reasons why CPU can be at 100%. I could really use a few pointers from people who are more experienced in this than me. At least a few pointers at how to identify the problem.

Thank you in advance.

You should be able to determine what is using up your resources by looking at Task Manager (through Ctrl-Alt Del).

Have you scanned for malware?

Yep. I've done a full system scan with AVG. Nithing.
I checked the task manager. In the processes tab the highest consumption is by stuff that should be consuming that much anyway. Like iexplorer which I am now using to view this thread. When I sort the programms by highest CPU consumption, the top are those programms that I am running currently. Its a bit hectic but never higher than 12. Fluctuates wildly between 1 and 10 for iexplorer and windows live mail.

In resource monitor overview, the highest threads are bu system: NT kernel and system (150 threads) The second highest is svchost.exe with 64 threads. And I have not a clue of what I just said. Sorry.

In the CPU tab, the highest avearge CPU of 40% is by svchost.exe

I am not sure what to make of all this. Not good with all this technical computer staff. Should have stuck to my bycicle.

Should have stuck to my bycicle.

lol - well, I do both, weather permitting - but not at the same time.

IE should not be consuming CPU resources when IE is just sitting there - even if you have dozens of IE sessions running, each with dozens of tabs. Same with svchost.

In Task Manager, under the Performance tab, you can start Resource Monitor that may help you find the culprit. Note that some 3rd party media players, like Roxio are famous for this. You might start in Safe Mode and see what happens too.

Now that I checked ieplore.exe in task manager, I detect 2 instances: one is using 54,000 memory and occasionally 1 or 2 CPU units. The other is at 6,000 memory and occasionally 1 CPU unit.

IE typically has two instances for each session because it uses the second for crash recovery - so that is okay.

After a bit of digging on-line I think I established that the problem is the "nt kernel & system". Not sure what it does but at least now I know what to try and fix.

Well, plugging nt kernel & system into Google shows a lot of people with this 100% CPU problem.

You might do some supplemental scanning with MBAM, or have one of our malware removal experts have a look - Please read this then start a new topic here.