Windows 7 Professional SP1 clean install CPU 100% spike

I have read similliar threads on this forum but have found no solution to my problem.

I recently installed Windows 7 Professional SP1 x64 on a computer I had previously running 32bit version of windows 7. I deleted the existing partitions and create new one, but after instalation completes i get 100% usage of CPU. It isnt always the same process that hogs the computer, it is usually currently active application.
Since the computer worked fine under 32bit system and i primarily installed the 64bit version only to utilise the full capacity of 4GB ram that is installed, my first thought was that the processor doesn't support 64bit technology. So i checked the Intel's site where it says CPU supports 64bits.

I would really appreciate all the help i get.

The computer specs:
Intel Core2 Duo E7500
4GB Kingston Ram
ATI Radeon Graphics

No i have not performed a virus scan, and it is still downloading and installing windows updates. I will report when it is done.

You did not need to upgrade to 64 bit to use all of 4gb RAM since any surplus is being used for hardware anyway. I always use 32 bit on 4gb and less RAM for best performance.

But now I'd wait to see how it shakes out once fully patched and with all the drivers Win7 wants after enabling Automatically deliver drivers via Windows Update (Step 3) and then running all rounds of Important and Optional Windows Updates, with reboots, until no more are offered when you again Check for Updates. This takes a few days to finish up.

Otherwise if you want to troubleshoot this or other issues most are covered in Troubleshooting Steps for Windows 7.

You can compare the install you did with the perfect install compiled in Clean Reinstall - Factory OEM Windows 7 which may also be useful for setting it all up using the tools and methods which work best for Win7.

I've recently done the same thing as the OP. Upgraded from 32bit to 64bit Win7 Pro. And the CPU is pegged at 100% utilization. I've scanned thru the other relevant posts on this topic and tried everything from disabling HD Audio in Device Manager to disabling System Restore (which may have worked a bit, it tends to bounce between 69% to 100% utilization). This started happening right after a clean install on a new partition and all. After about 4 days, was finally able to get the drivers and windows updates completed. Nothing else has been installed to this point, just Windows.
Unfortunately, all of this has really done nothing - are there any new insights as to what's causing this, or ways to fix it?

Did you do a perfect Clean Reinstall Windows 7? If you forced a bunch of drivers, then I'd do it over because this is a driver-complete OS, not XP. You can make it a diagnostic install by getting online to install all Updates after install only, testing performance between each batch until they are done. Only then install programs one at a time with time to test performance between each. Likewise settings changes. Try to pinpoint when the problem begins.

Try establishing a Clean Boot, test hardware, check for infection, use the System Resources all detailed in Troubleshooting Steps for Windows 7.