Recently upgraded my 500GB HD to a 1.5TB Seagate HD. Included with the Seagate was a cloning program powered by Acronis (which I have had good luck with in the past). I did a full clone to make a new bootable drive. When I first cloned my C: drive and then booted to the new drive, first thing I did was right click on the new C: drive and compared it with the now D: (formerly C: ) drive. All was good, I knew the numbers wouldn't be exact but they both roughly said "242GB used" on each drive. That was yesterday, and I left the PC on for most of the day/night just to make sure the new drive was okay. This morning I booted on, and all seemed fine. However when I right click on my new C: drive, it now says "185GB used"! Right clicking on D: still yielded "242GB used". 57GB gone! So in a panic I ran all my programs, and looked at much of my data (pics, music, etc.) and everything seemed to be there. I couldn't account for where 57GBs went off to. I clicked on the most important folders (Windows, Program Files, Users) and compared folder sizes. All were comparable between the C: and D: drives. So I did a weird thing. I went to the top levels of C: and D: (so I could see the entire folder structures of the drives). I have "view hidden files" enabled, so I see the translucent hidden folders as well. I clicked "Select All" on both the C: and D: drives, thus selecting all files folders, including the hidden ones, then right-clicked and selected Properties. All folders on C: = 176GB All folders on D: = 175GB I've installed a new program or two so I can account for the 1GB difference. But what I want to know is: why is there 9GB of "superhidden" data on my new C: drive (which is the only reason I can account for the 185->176 difference) and more importantly why is there 67GB of "superhidden" data on my D (old C drive? (242-175) And why was it there when I first cloned, but is gone from my new C: drive now? Anyone got any clues? I know Vista does some kind of Restore Points and shadow archiving [the HD is almost always running], but could that really be 67GBs of archiving in "superhidden" [ghost?] files? And if so, why would those 67GBs of ghost files be brought over on the initial clone and then disappear within a day? Maybe an important point: I'm running Vista 32-bit Enterprise edition (kind of like Business edition but given to large institutions whose people work from home, which I do) - perhaps Enterprise does more "hidden backups" because it's designed for corporate use?