Did this with my acer this year.
Standard Windows utility that is called CONVERT serves this purpose
Just go to the Command Prompt and execute the command:
C:\> CONVERT C: /fs:ntfs
Where C: is a name of the drive you want to convert.
After machine re-boot conversion process will start and you'll have your FAT32 converted to NTFS without of data loss
edit: To open Command Prompt, click Start, click Run, type cmd.