Try this quick tip to regain some space. We use SCCM to deploy Windows updates and they can fill your C: over the life of the box. We use these two methods to reclaim space:
Empty all the recycle bins for all users
For Windows 7 or Server 2008 enter this command:
rd /s c:\$Recycle.Bin
For Windows XP, Vista, or Server 2003 enter this command:
rd /s c:\recycler
Method two open Control Panel > Configuration Manager > Cache Tab > Configure Settings > Lower that slider to less space to less less room for updates to stick around > hit delete files > Check ‘delete persisted cache content’ > hit yes
This week I gained back about 16 gig of space on a C: that had 0 MB remaining.