It does sound like the Linux installation has damaged the partition table. Possibly (Hopefully) it just resized your C: drive too small, so you won't have lost any data or overwritten any files. You could try to access the C: drive from the Windows installation you've got from "My Computer", if it's there. If not, try a Dos box (to get one, go to the start menu, click on "Run Program" and type in "cmd".) That way you can at least check to see if your data is still intact. You should be able to run one of the partitioning utilities on your working Windows installation - it's a long time since I've had to use one in anger, so I can't give you any recommendations, I'm afraid.
The Linux installation will have set up at least part of your system disk as a Linux file system disk. The Windows installation disk doesn't recognise that, so it will report it as unallocated space. A Disk partitioning utility will report the Linux partitions as "ext4" or (less likely) "ext3". If you delete those Linux partitions and increase the size of the Windows C: partition (it will most likely be the first partition reported on the partitioning utility), hopefully you should be able to start Windows normally - provided none of the data or files has been lost! Good luck, there should be someone along to give you better advice shortly. Let us know how you get on, or if you've got any questions, someone should be able to give you a few tips.