bus speed lowered automatically [ Edited ]

[sturr]

compaq presario desktop SR5401UK, product number KN265AA

Vista home premium service pack 2

32 bit, AMD Sempron Dual Core Processor 2100,  GHz

3 GB RAM

Hiyas, please help

no error messages,  no BSOD ever.

I installed windows updates almost 2 weeks ago and since then the pc has been far slower than before. Programs hang, don't respond, even windows explorer.  I've done all the scans for malware, viruses etc etc  and came up with nothing much, just JAVA_DLOADR.BCO which was dealt with. 

Did all the diagnostic and hardware scans too, nothing wrong. Optimized pc with a program, all is fine.... but it isnt...

Did a system restore to before the updates, made no difference.

CPU fan started making whirring sounds, sometimes for no reason I could see, so today i replaced the heatsink and fan = cooler and quiet, but still the same problem with slowness.

A  friend said run CPUID CPU-Z , it came up with the wrong processor name (said it was 1210, not 2100) land said the bus speed is now 200 where for my machine it should be 1600 according to the HP site.

MAYBE because of the failing fan  the cpu overheated and the motherboard lowered it automatically to prevent further damage? that would explain the slowness.

I can't check what it is now or change it in the BIOS, because of HP's wisdom in making that inaccessible for the owner. Unless there's another way.

What can I do?

Just tried resetting BIOS to defaults, made no difference.