I am currently running windows XP but would also like to have windows 2000 on my machine. How can i have a dual boot with both the OS. Or can I roll back to windows 2000 just without XP?

You can dual boot. I'm presently running 2000/XP myself. I prefer to have my operating system's on separate partitions from any other data storage, application or OS partitions so I created a separate partition for XP when I went to install it. However you prefer things...do them that way. So if you want everything all on one partition, go for it. Whichever way you decide to do things, all you need to do is stick the 2000 CD in and boot to it and begin the install. Once you're finished installing, you will be dual-booted.

Careful... When you run setup and install W2K it will disable/replace the XP mbr/boot-files with the W2K version(s), and thus you lose access to XP. (XP arrived in M$-land after W2K - so W2K doesn't know about its distant cousin...) If going for a dual-boot: To recover XP and thus complete the dual-boot, run XP setup repair routine; allow it to repair/restore XP mbr/boot-files. As CurtR suggests - each in its own location (partition/logical-drive) is preferable. If you don't already have a separate location for XP, then use PM/SC to create one? If intending to 'roll-back' as it were to W2K and lose XP... just install W2K to same locations (C: Primary) as XP. As indicated already (above) it will disable XP. You can locate/delete XP folder from the drive (via W2K Explorer). Since the folder name winnt is already in use in that location for XP, W2K will probably go in as windows; or you can change the offered default to be whatever you want - perhaps winnt-2 or W2K (but not winnt)? If you wanted to start afresh for a dual-boot, then perhaps use the model in post-21665 (#5) on this W2K forum. It details a dual-boot for '98/W2K; replace '98 with XP, and install W2K first, and you have it. Installing W2K first avoids the issue of having to 'repair' XP mbr/boot-files; XP in last automatically rewrites W2K mbr/boot-files to XP level and takes over control of boot-sequence.

A much easier way of recovering the XP multiboot is copy off to a temp folder two files, ntdetect and ntldr. Once complete with the W2K install boot up and replace these files at the root with those you saved. You will have to edit your boot.ini and add the xp entry [or back it up also and then copy and paste it into the w2k boot.ini]. Once complete reboot and you will have your choice of OS. You do need seperate partitions since both contain a winnt folder.