There are several barriers on hard drive size for Windows ME. As it relies on the BIOS for addressing, it suffers from the same limits on hard drive size as the BIOS. Here are the important ones:
127 GB barrier (hardware) - Most PCs of the era that Windows ME was released do not support more than 127 GB hard drives - the extra capacity will be unusable.
127 GB barrier (software) - Windows ME itself cannot address more than 127 GB natively. There are special patches that will allow it to address more. You will also need to use a third-party tool to partition the disk.
2 TB barrier (FAT32 implementation limit) - The FAT32 file system as used by Windows ME cannot be made larger than about 2 TB. However, you can divide the hard drive into partitions, so you should still be able to use disks larger than 2 TB. At this size, the limitations of the FAT32 file system really start to come into play, and defragmentation will take several hours.
The minimum requirement to run Windows Millennium are as follows: Pentium 150MHz Processor 32MB of RAM 320MB of hard drive space
You will need to change your BIOS settings so that the hard drive is run in "Legacy" or "IDE emulation mode."
There is no upgrade path from Windows ME to Windows 2000. You would have to reformat the hard drive to remove ME before you install Windows 2000 from scratch.
Windows xp supports a maximum of 4 gigabytes of ram and 2 Terabytes of hard drive space
4.
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.
The hard drive stores the Operating System. Like for example : Windows XP or Windows Vista or even Windows 7 without the hard drive your computer will not turn on.
Yes. NTFS, the file system that Windows XP uses, has a maximum partition size of 16 TB.
Windows XP has no bearing on the hard drive size beyond what is needed to store it. Thus a hard drive on which Windows XP is installed can be anywhere from 1.5 GB to 3 TB.
Yes you can have the Mac OS on one drive and Windows on another drive. Or you can partition a single hard drive and have both on the same drive.
You can certainly move Windows to an external hard drive but Windows will not boot directly from an external drive. If you are running Windows in Parallels (See links below) you can have Parallels installed on the Mac's drive and then have your Windows virtual machine on the external drive.
Whether or not the hard drive has Windows installed on it is irrelevant to the actual process of replacing the drive. if you want to preserve the current Windows installation, you'll need to use hard drive imaging software to copy the data from the old drive. Otherwise, you can simply replace the drive and reinstall Windows as you would normally.