Windows 7: System crash after incorrect ubuntu dual boot

Hi again i search the advice of the professionals.... My brother yesterday installed Ubuntu on my computer but he did not use the new partition i setup for him to do it.
As a result Ubuntu was installed on the C drive which is the mean partition for my windows 7 computer.
Now the laptop starts up in error mode Showing the following error
error: unkown filesystem.
grub rescue -
As i used to run Ubuntu before it is clear to me what happened. Dual booting totally incorrectly overwrote my windows partition. I know i can try to make linux boot but i don care about that . I need windows 7 to run!
I tried booting the pc with Hirens boot latest edition, tried running it from cd rom after changing boot setting to cd rom at first then i tried with a usb stick. No result; Still the same error
After Hirens i tried booting with an Active X cd stil lthe same thing not booting stil the same error
Windows 7 recovery boot options like F8 are not accesasible anymore....
As i have an ACER COMPUTER i made 4 back up dvds via the acer recovery tool;
Also these Recovery dvd are not running and i doublechecked START CD AT FIRST IN BIOS
The acer dvd recovery cd are in a fine condition no damage. I don t have a windows 7 cd did not come with both my computers as they are both acer home premium;;;

I s my computer ****ed or is there anyway i can recover my windows 7 installation



luckely i haven another computer running winows 7.

Anybody who does have any advice i am already thankful in advance ..
Seriously