you cant convert without losing data
you will have to back up your hard drive contents with a program like driveimage XML (free) then copy the drive image to a diff hard drive >>>> then I suggest you use a free program like killdisk to wipe this drive / then reformat the drive using NTFS file system and basic disk protocol
then use drive image again to restore the data to the drive
rather strait forward process actually
the drive image will consume approx one half the drive size of space where ever to deciede to send the file
example
I have a hitachi 250 gig drive I want to image >>>> I will send the image to my seagate D drive >>>> I must be ready to consume 125gigs of space on my seagate drive