It is not a "problem." It is perfectly normal for the amount of free space to decrease as more files are added to the system. Windows Vista's System Restore feature takes periodic snapshots in order to facilitate restoring to a previous state. This process will use an increasing amount of space, though eventually the amount of space used will remain constant as old backups are deleted and new ones are put in their place. if you do not desire this functionality, you can turn it off.
The Vista tool used to encrypt an entire hard drive is BitLocker Encryption.
There is no "DOS mode" for a hard drive, and it is not necessary to use DOS to format a hard drive. Vista's installer had a built-in partitioner and formatter.
No. Vista ruins all windows(non-vista) and RAIDed partitions.
The main drive is the drive with your operating system on it.
Just insert your Vista DVD and start installation from Windows Xp, choose new installation and choose that hard drive where to want to install Vista (your second hard drive). Vista will make all required jobs including boot screen to choose which OS to boot. Before you start, please, bakc up all your data from your hard drive(s).
Yes. The SATA internal hard drive in Vista can be turned off, by turning off the feature in system BIOS.
reformat the computer.
Sounds like a problem with Windows XP. What you should have tried to do is take the original hard drive, put in the xp install disk, to the install, choose to format the hard drive, and then continue with the XP install. BTW: XP > Vista. Linux > XP. You should install Linux, instead of XP.
Yes, you certainly can. Install Windows Me first on one of the hard drives. And after that install Vista on another hard drive. If you do reversed multiboot will not work. And you will have to edit boot.ini file manually which is not that easy.
Yes. Any hard drive, flash drive, or other external storage device that conforms to the USB Mass Storage device standard will work on Windows Vista.
There's no such thing as Windows XP format or Windows Vista format. You should check however if your external hard drive uses an NTFS or FAT32 partition table. You can see that by right-clicking the drive (C, D, E, ..) and clicking properties. If it uses NTFS it will be no problem for Vista. If it's FAT32, then google for a way to convert it to NTFS. No big deal.
Yes. Actually, there is no need to remove the hard drive. You can format the existing hard drive and install XP on it as well. Note: Yes, you can there is no need to remove the hard drive. You can format the existing hard drive and install XP. and also you can install both opreting system single computer. XP and vista both.