I was facing same problem
Problem:
I right clicked on my c:drive (on which i had my windows7 installed) and checked option compress this drive to save disk space
Rightaway didn't happen anything till the moment i restart my computer
Now I was completely stuck as u r.
I didn't want to format my c drive n reinstall windows7 cause i was having some useful data on my c drive.
Solution:
I went to my friend who is quite geeky , but he also gave up.
Finally , I went to hardware store.
1.He pullout my harddisc .
2.Plug it to diff. PC as a external Hard Disk.
3.Now he right clicked on the c:drive(drive in external hard disk which was c:drive on my laptop ,on his PC it was drive after his last drive ).
4.Went to properties n unchecked checked option compress this drive to save disk space.
5.hit apply it will take some time son wait.
6.Then i connected hard drive back to my laptop.
7.Now everything is was fine.
8.Hard disc was checked n now everything was ok.