[WIN7] Re-sizing partitions. Does it work?

Hey all, Friend of mine has a Dell lappy with a 300GB HDD. For some unknown reason, the C drive is a 60GB partition, and then it has a 230GB D drive, plus a 10GB recovery partition. Needless to say, there is 0 free space left in the C drive. I know Win7 has a tool to resize partitions, but does it work without nuking the data? Reading the help section on it didn't really make it any clearer. One would think that you would need to shrink the D drive to open space to expand C. There is plenty of free space to do that. Has anyone tried that? I hate to experiment on someone else's machine... Thanks