You doing something wrong.
You don't need to create a disk.
You need a usb flash drive that you copy FRST to.
Plug the flash drive into the infected PC.
Then boot the computer up as instructed at the link below: (I put that up last night)http://maddoktor2.com/forums/index.php/topic,55928.0.html
Restart the computer.
As soon as the BIOS is loaded begin tapping the F8 key until Advanced Boot Options appears.
Use the arrow keys to select the Repair your computer menu item.
Select US as the keyboard language settings, and then click Next.
Select the operating system you want to repair, and then click Next.
Select your user account an click Next.
Continue with on as outlined in step #3