Install Dual Boot Windows XP and Windows 7 in 1 Hard Disk

Need 2 OS on 1 disk. Wanted to keep Windows XP but want to try the latest Windows 7. There is a simple technique to install the 2nd OS

Preparation before installing, and installing Windows XP

The first step
To partition a hard drive with 2 partitions or more. At least 2 partitions, C and D. Partition C should use the FAT format. For example, only use a maximum capacity of 30GB for Windows XP.