CPU at 100% and down to 1 processor on a duo core

hey all
I did a clean Install on a new HDD yesterday, all went well I thought
it was running ok last night responsive and quick I turned her on this morning and it hung up on the boot screen then hung up on the black screen with the pointer (between log on and desktop)
finally gets up to the desk top and its black with icons, I ran msconfig
looked in boot / advanced options/ looked at my start up processors clicked number of processors where it usually offers 2 it is only giving me 1, The alert went off in my head, went to task manager, cpu usage is at 100% i am idle this makes it impossible to do anything I am at a loss what is causing this, I did nothing but install some apps like win rar and my Tune up utilities, start up is limited to what i need at start up windows ,kaspersky,and my synaptics touchpad, I am confused, any suggestions are welcome, will try uninstalling Kaspersky as a start since i have had a problem in the past......Please help!!!

Did you check the bios to see if the cpu was detected correctly? Check what the cpu temperature is showing as well. If it's too high check that the cpu cooler is on properly.

Every time my computer started up & stayed at 100% CPU usage it was because of driver conflicts!
So something you installed has some drivers that don't agree with W7 at all!
Start uninstalling programs that you installed last & see if it stops & what program is causing it.
OR if you have system restore still enabled, try last known good cfg or restore to an earlier point & see if that fixes it.
If it does, then see what program causes this by installing them one at a time & reboot after each installation until the problem returns...then you'll know what it is & not to install it or look for a recent program patch for it.