It is possible to actually format the C drive, and restore (retain) the current Windows installation! It's quite tedious and takes more time than converting but, at the end you have more advantages than converting. Converting will slow down your system further, as it converts to 512 bytes cluster size of NTFS file system. Formatting using the default cluster size almost always means it is 4k (for extremely small partitions it may be 2k or less), which makes your system run faster and reduces fragmentation greatly. Anybody knows (the step-by-step procedure of) how to format the C drive to NTFS while not losing even a single bit of the current Windows installation? (Of course formatting the C drive will mean you'll lose all data on it, but the trick lies in having a second clone copy of all the data.) Valid answers posted as of 26/9/06: 1. Use Acronis True Image (Step by step instructions not provided yet.) Post your answer here. I'll post my own answer after some time (min 7 days but upto 1 month depending on the flow of answers).