If your PC is unable to boot back into Windows 7 after installing a loader don't panic, simply do the following.
1. Boot up your PC from your Windows 7 installation disk
2. Select Repair your computer option
3. Select to open Command Prompt
4. Input following command and hit enter
bootsect.exe /nt60 c:
5. Restart your PC6. If it still doesn't work, try the following command
bootsect.exe /nt60 all
7. If you are using the default loader then press the Escape key (or R) during the boot process and select Windows without loader.