I think this has something to do with the oem licence of Windows. Tiny probably put a hidden partition at the back of the HDD which allowed the the reload disc to put the computer back to it's original state(i.e.) as it was when you bought it. Wiping your HDD will have destroyed that partition and I would think render your Windows useless as it was 'tied' to that machine.
If you don't really need a Windows system why not try installing a version of Linux. Does everything Windows will do, and using Wine ( a Linux app) you can run most Windows based games. Have a look here:-