How can I find C:\ and retrieve Windows files from Parallels on a Mac?

Friday, 15 days before, I worked in Windows 7 using Parellels 5 on a Mac (Snow Leopard) desktop computer.
I don’t know what happened, but when next Monday I tried to get into Windows, I couldn’t do it. It gives the “setup is starting…” on the Windows 7 wallpaper, and in the taskbar says that Parallels tools are not installed.
When I try to install the Parallel Tools I have to put some GB on the HDD, which is 64 GB, but I’m afraid that perhaps I lose some data, even if I don’t know for the time being, where is located this data.
Can somebody tell me where is my C:\ disk? And how I can find all my Windows partition, to copy what I don’t like to lose? Please!
I tried to put a new VM, with a new version of Windows 7 and as key I wrote xxxxx.xxxx…., and on the Windows desktop opens a window where is: “The unattend answer file contains an invalid product key. Either remove the invalid key or provide a valid product key in the unattend answer file to proceed with Windows installation.”
I don’t know where these files are to change them. Also the old VM, does not open, and gives the same “unattend answer” error.
iMac configuration :
21.5-inch: 3.06GHz
1920-by-1080 resolution
4GB (two 2GB) memory
500GB hard drive
8x double-layer SuperDrive
ATI Radeon HD 4670 with 256MB

Please Help.
Thank You.
chris1948

 

Greetings, chris1948.

Be advised: the moderators may move this thread to the Macintosh forum.

Are you sure you have a valid Windows key?

 

Thanks Caliban.

Of course I have the valid key.
Any idea in the way to proceed?

chris1948