For that you need a bootable CD of your operating system. A bootable CD means that your PC will boot with that CD rather than your harddrive.
CAUTION : You will format you PC completely and lose all installed data in installation drive.
Insert your Windows CD or DVD and get to the part where it shows all your partitions and delete the Linux partitions. If you are unsure which one is your windows partition just make sure you don't delete or format any partition that is in the NTFS, or in the rare case a FAT32 format, as those would be your windows partitions.
You will need at least two partitions.
Disk Management
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yes you just simply make separate partitions.
Windows 1.0, 2.0, 3.0, 3.1, 95, 98, and ME can support a maximum of 26 drives or logical partitions. Windows NT 3.1, 3.5, 3.51, 4, 2000, XP, 2003, Vista, 2008, and 7 can support several thousand drives / partitions in a system.
Always should the drive be partitioned. As NTFS for Windows 7. You can edit partitions while installing Windows through the installation menu or command prompt, or in diskmanager after the operating system is installed.
back up everything, remove ALL the partitions, then recreate the partitions you want to keep
The minimum number of partitions needed to dual boot windows xp and windows vista is actually 2, one for each operating system. However, if your computer was bought and it already had one of those two systems preinstalled and with it a separate windows recovery partition as well as a system reserved partition, then your minimum in that case would be 4 priamry partitions (which also happens to be the maximum allowed if you are using strictly primary partitions. One way to have more than 4 primary partitions is to have one of those partitions become an extended partition which can in turn have as many partitions as you need. I hope that wasn't too confusing
Yes, you can do it, but firstly you have to install XP and Windows 7 must be installed afterwards. Moreover, you must create two partitions to install them.
No. Vista ruins all windows(non-vista) and RAIDed partitions.
You can remove password on Windows 7 after you sign in by going to control panel and then selecting user account and from there you will find an option to change or remove your password.