Flashing my BIOS and Vista Ult. 64Bit OEM

I have just flashed my MSI K9A Platinum motherboard so that it will recognise
my AMD Athlon 64 X2 AM2 6000, as it used to recognise it as an "AMD
unrecognised processor" or something along those lines.

Now because it thinks I have changed my Hardware I have to reactivate Vista
64Bit, so I try and all I get is "The product key you typed is already in
use", with the option of buying a new key, using another I "already have",
using a phone activation service (which I don't think will help) or contact
Microsoft support (which I have to pay £46/$92 for, because I have had my
Vista running for more than 3 months).

Can someone please tell what to do as I am not paying £46 pounds for tech
support, when it is the naff activation system which is at fault.

Any help would be appreciated, thanks in advance.

PS My Vista will shut down in 3 days if I don't get something done.