Installing TL-WN821N now causes continuous starup loop of death

I won't start about how gutted I am that I bothered installing Win8 over a perfectly working install of Windows 7; the wireless usb adaptor didn't work when I booted into win 8 and I followed suggested instructions for the forums to refresh the driver installation. Now the computer boots into an error (says it's gathering information and reports a "irql not less or equal" error and reboots automatically before getting to the login screen, but then reboots to a maintenance screen of which none of the options work - the command prompt reports that the file system is locked, and only helpfully suggests that it can reset your whole computer by removing all non-app store programs! What a complete piece of junk; I now have a youngster who's bereft at not being able to play his games, all for nothing.

I've tried booting into recovery mode (shift F8) but it doesn't provide the extra button I've seen in other pics in advanced options. Any suggestions how I can reverse back to win 7 whilst preserving my files/programs - at this stage I don't care that I've lost $40 on crapware.