It doesn't take but a couple of minutes to reinstall Ubuntu, so I'd try that. When I had a similar problem with Mint Linux, I reinstalled it and both Windows 7 and Linux came back and worked. I got into my problem by trying to resize a partition I thought had nothing to do with either OS, but when Linux is installed, you can't resize anything.
Iam right on Ubuntu Live cd I had Window7 and Ubuntu 12.04 on my system,as i was going through Linux lesson my grub got deleted and iamnot able to recover, the code in linux lesson was
After executing it i rebooted my system so now when my system start it shows
grub1.5 please wait ....
and its stop there,so i think i have lost my grub loader,as i was going through linux lesson before i also executed some command
Please help,Iam right now in Ubuntu live cd, i can't even access my Window7