That doesn't make any sense.
Certainly a system will lose some performance over time, but the Level 2 cache is effectively used as a short term scratch pad by the CPU and a clean install of Windows will make no difference to how these are utilised.
Benchmarking on a 'well worn windows install' would give inconsistant results as how do you know each install has been subjected to the same kind of punishment.
Clean installs give a level playing field.
A Core 2 Duo E6600 system owned by someone who fills it up with spyware and viruses along with a thousand and one bloated trial programs will certainly be slower than a well maintained X2 6000+ system, and visa versa.
Intel paid off the entire internet?
Fairly sure most sites out there would take exception to that.
3.43GHz on stock voltage, care to share a CPU-Z shot of that with verification?
Not saying the 6000+ is a bad chip but take a reality check, because you sound like a troll.