While I understand that you have got a code, and should have a disk, and that your copy of Windows is legal, that download is not. This will probably mean that you cannot install Windows Updates, some of your favourite software, and the whole thing is just one massive virus waiting to steal your Credit Card Information. It would therefore be ideal if we could just fix this using only legal software.
The download I provided is completely legal, and should be sized at about 120mb.
Once you have downloaded it, using the instructions at the bottom, you should either copy it onto a CD (ideally) or a flash drive. Make sure to format it (normally) so that all other data is deleted (back it up first) first.
Then, put it in, restart your computer, and go into the one time boot menu. You should then be able to select CD/DVD or USB Memory Stick (or similar) It is recommended to plug the USB memory stick directly into the back of your computer.
There should be nothing to stop this from working, and once it has loaded everything, put in your language, click Repair my Computer at the bottom (Install will NOT work for this disk, the files have been removed to make it legal) and then do a System Restore, as in Method 2 here: System Restore - How to
Good luck, and if you still have problems with this, do not be afraid to ask.