Grub rescue, unknown file system. Can't boot into Windows 7

GRUB works in stages. First part of it is loaded from MBR (Master Boot Record), which points to secondary data located on your Linux partition that is required to proceed with next step of grub. From your description of the problem, apparently you have deleted the second stage of your grub installation and grub isn't able to find it.

In order to get back your Windows 7 boot loader on your MBR, to allow you to boot into Windows 7, follow these steps:

1- Boot your computer from your Windows 7 install dvd.

2- Choose your language, time, and keyboard input on the first screen, and click next.

3- On next screen, you will be presented with three choices. Click on "Repair Your Computer", to enter recovery window. Now select "Command Prompt". At the command prompt, first change your directory to boot (cd boot), and then type "bootsect /nt60 C:\". This will restore your windows boot loader onto your MBR.

Now restart your computer, and you should be able to boot into your Windows 7 installation.

Since you don't have the installation disk, reinstall Ubuntu. This will fix GRUB and you'll back up and running.

After you have done this, you can make a recovery disk in Windows, from which you should be able to reinstall the Windows MBR (Master Boot Record). Don't delete the Ubuntu partition until you can boot directly into Windows without going through GRUB.

The simplest solution would be to find a disc (borrow it from someone), but this should work.