Old HDD with OS installed in a new PC. Any tips?

Hey guys, I'm about to build my second gaming PC, this one is to be my main PC (once it is built).

So I was wondering, is it possible to use the HDD from my current PC in the new build, leaving the OS and games already installed on it?

I mean I'm guessing it, so long as once I boot up the PC it set it up in the Bios to boot from the HDD, but would I have any problems with Windows 7? 


It may seem stupid, but I'm not to sure.

So any help is good, thanks guys.

Generally, that doesn't work. 90% of the time the new computer when trying to load the OS from the old machine will BSOD. If it does manage to load the Image you will have massive driver issues and its more of a headache to make it work properly than it would be to reload the image to the new machine and deal with re-installing everything.

Yeah..  Just backup your saved game files and whatever else you need and start fresh.  It's not worth trying to migrate to new hardware. 

Probably be easier to jsut upgrade some parts on the current build then?

Depends on what you have already..  If you're upgrading to Windows 7, I'm assuming that the compnents of your build now are outdated as well.  So you gotta wiegh the cost vs performance gain you can expect to see given the compnents you have now.  (Is your PSU adequate to run a new graphics card?  Will your current cpu bottleneck your new gpu?  How fast is the ram etc.  I'm not an expert but there's only so much you can upgrade efficiently and cost effectively on old systems.)