When you want to resize the disk in Windows 7, server 2008 or server 2008 R2, you might get this warning:

Error: there is not enough space available on the disk(s) to complete this operation

This could be fixed by the following guides:

1. Right click on my computer
2. Click on Manage
3. Goto storage
4. Click on Disk management
5. Right click on disk management and click on rescan disks
6. Try to resize the disk again