Mac Info: Model Name: MacBook Pro Model Identifier: MacBookPro7,1 Processor Name: Intel Core 2 Duo Processor Speed: 2.66 GHz Number of Processors: 1 Total Number of Cores: 2 L2 Cache: 3 MB Memory: 8 GB OS 10.7.4 Okay so my original MBP came with a 320GB HDD, A few months ago I was able to get a 1TB HDD that I planned to upgrade to. Using SuperDuper I copied everything from the 320GB HDD to the 1TB HDD. It's been running for 6 months with no problems whatsoever. Last night I noticed that I finally reached 10gigs until the 320GB Partition was full. Sources tell me that Disk Utility allows Partition size increases without deleting data. This is what Disk Utility shows me. http://cl.ly/image/3G2W2R3c1I0T I increase the partition size to 999.86GB and apply it. http://cl.ly/image/2E2n3U2a0433 The progress bar at the bottom states that the resize is completed without a problem but it always reverts back to the original 319.21GB partition. And any size besides 999.86GB will give me this error. http://cl.ly/image/2r3f3v1F0T2h The only problems I've been able to find is if the HDD isn't using Partition Map Scheme : GUID Partition Table (Which it is) So I'm completely stumped.