Boot with your Win7 installation CD. When prompted, press R to repair or select repair in the GUI if that apears, select your Win7 installation to repair. Probably #1
Enter the administrator password if you are prompted for it.
To repair the MBR, type in this command: fixmbr hit enter
You will get some prompts, type Y and hit enter to carry out the repair.
Type exit to leave the console and then reboot.
You will loose the dual boot for WUBI into Ubuntu, but it will/should get you back into windows bootup. If you are triple booting you may loose that as well.