System freeze in normal mode

I have a Toshiba Laptop running Windows XP SP3, with 2Gb mem. My problem is that about a week ago after I boot the system and it loads everything, my CPU utilization jumps to 100% and stays there. The system then becomes non-responsive to everything (Keyboard, mouse, etc.) and takes forever to run anything. For example, if I simply opened Task Manager, it would take hours to load. I have run Spybot, Adware, Malwarebytes, all with no apparent serious problems other than the normal cookies, which I deleted. I run Avast virus protection and have a home network going through a Linksys router. The strange thing is that if I start-up in Safe mode, everything seems to work fine. I have also run HiJackThis and have the log. In my attempts to resolve the problem, I also got a message about MSI Installer and MS Visual C++SP1 (when I tried to install newer version of Ad-Aware), but do not know if this is related to my main problem. Any help would be much appreciated.

Since it runs better in Safe Mode, most likely something is starting at boot that is causing the problem.

Use msconfig to determine what is causing the problem.

These are good tutorials on using msconfig in XP or Vista:
How to use msconfig in Windows XP
How to use msconfig in Windows Vista

Click on Start then Run, type msconfig and press Enter.
Click on the Startup tab, record what is currently starting then click the Disable All button.
Reboot and see if it runs normal.
If yes then use msconfig to enable several items at a time till you find the culprit.

If no, boot to Safe Mode again, start msconfig and click on the Services tab.
Check the Hide All Microsoft Services box, record what is currently starting then click the Disable All button.
Again, do a regular boot, see if it runs normal.
If yes then use msconfig to enable services till you find the culprit.

Once you've found the culprit, uninstall it or find out how to eliminate it from your system.
Simply disabling it in msconfig is a temporary fix at best.
Enable everything else you disabled.