Win7 Activation - OS thinks it is pirated!

Hi,

My Windows machine was getting really slow, so I decided to do what many people are doing - get a faster HD and put the old drive in the DVD drive bay.

I backed up my old drive (both full backup and bootable backup on an external disk. As my original version of Windows came pre-installed on my computer, and I didn't want to do a factory restore onto the new disk, because it came with loads of HP bloatware, I downloaded a legal iso of Windows Home Premium and burned it onto a DVD. (downloaded from PC World article 248995 how_to_install_windows_7_without_the_disc)

I then installed the drives and put the new system on the drive, and input the serial from the sticker at the bottom of my computer.

I formatted my old drive and installed it into the optical bay.

Now everything is working great, it boots up in no time at all. But the windows activation thing kept popping up saying the serial is invalid. As far as I know what I have done is perfectly legal. I disabled the software protection at startup hoping it would just go away, but now it is telling me explicitly that I have pirated software....

Anything I can do to solve this problem? Would much appreciate any help!

Peter

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Home Premium, Service Pack 1, 64 bit
Processor: Pentium(R) Dual-Core CPU T4300 @ 2.10GHz, Intel64 Family 6 Model 23 Stepping 10
Processor Count: 2
RAM: 3998 Mb
Graphics Card: Mobile Intel(R) 4 Series Express Chipset Family, 1807 Mb
Hard Drives: C: Total - 715404 MB, Free - 682650 MB; D: Total - 305242 MB, Free - 274842 MB;
Motherboard: Quanta, 3069
Antivirus: Microsoft Security Essentials, Updated and Enabled