People format the partitions on their hard drive, for various reasons. They sometimes do it, to get rid of harmful viruses and malware that has eaten into most of their files, or just for the creation of a new format, in which case it is called re-formatting. In both the cases, the data present on that particular partition, is bound to lose all the data present on it, if proper backup is not taken.
A format is similar to a file deletion operation, as the data is not deleted permanently, instead, the disk space occupied by the data, is now marked as free space in the file table entry, hence making it inaccessible, by the operating system. You can recover data from formatted drive, provided the data loss is purely logical. If the data loss is due to physical damage to the hard drive, then it is advised that you use a good data recovery service for recovery of all your lost data.
A PC running on Windows operating system might be using either NTFS or FAT file system. REMO Recover (Windows) Pro Edition software lets you recover data from formatted hard drive the file systems with utmost ease.