How much RAM do you have assigned to that VM?  Use TreeSize to few the contents of C:, which can also see the size of the Page File.  The Page File, if Windows is managing it, will be around 1-1.5 times the amount of memory.
Hello,  I've setup Dell's ESXI 5.1 image on a R720 with a 146G Raid 1 configuration. I split the drive for 2 VM's at 60G  each. I've only installed 2008 R2 and did all of the updates and I'm now left with only 9G of free space...can anyone tell me where I have gone wrong? I can only see 22G in all of the folders on the c drive. Where have the other 28G gone?
ESXI 5.1 setup too large