My Pentium III computer is set up to dual boot either Windows Professional 2000 or Windows 98. Windows 98 was the original operating system. The dual boot mechanism was set up automatically when I installed Windows Professional 2000. Now I would like to uninstall Windows Professional 2000, but am not sure how. Can you advise? If it is too complex to uninstall Windows Professional 2000 could you advise me how to change the boot menu default selection to Windows 98 rather than Windows 2000 Professional?

This procedure can be a bit tricky. You should (I really mean must) backup important data before proceeding, in case the procedure goes wrong and you need to completely reinstall your system (which is a genuine possibility with procedures like this). Your backup MUST include, but not be limited to, any data you wish to keep which is on the Windows 2000 partition, as there is a chance we will delete that partition in the process. If you don’t like the sound of this and would prefer the other option, namely making Windows 98 the default operating system, then skip to the bottom of the answer.

What we will do is remove the Windows 2000 files and the boot-loader (which is the menu used to select the operating system to boot). Windows 2000 and Windows 98 will be on two separate partitions. I assume that Windows 98 is installed on the C: drive. If it is not, do not attempt the following procedure and contact me again with the drive letter for the Windows 98 and Windows 2000 partitions. Assuming that Windows 98 is on the C: drive (as it should be since it is the original operating system), you need to start by creating a DOS boot disk. Boot into Windows 95 and insert a formatted blank disk into your floppy drive, open a DOS prompt and type ‘SYS A:’ This command will copy system files to your floppy disk and it will be bootable. Now copy the files SYS.COM, FORMAT.COM, FDISK.EXE, ATTRIB.SYS, and DELTREE to the floppy disk. You should find these in the C:WINDOWSCOMMAND directory. If not, search the hard drive for the files. Before going to the next step, it is necessary to establish if your Windows 2000 partition is FAT or NTFS. Go to ‘My Computer’ and find your Windows 2000 hard drive. Right-click on the drive and check the ‘File system:’. This will be needed later. If the Windows 2000 drive is not visible don’t worry - that means it is probably NTFS.

Now reboot the computer and let the computer boot off the disk to a DOS prompt. Once the command prompt has appeared, type the following command:
SYS C:
This will return the computer to the Windows 98 boot loader and will overwrite the Windows 2000 boot loader. After you have executed this command, the Windows 2000 files can be deleted. If your Windows 2000 partition is NTFS, you cannot delete the files from the command prompt as the boot disk only supports FAT and FAT32 partitions. If this is the case, you will need to run FDISK and delete the Windows 2000 partition. The partition will be labeled as unknown in FDISK (as it doesn’t support NTFS) but you can still delete the partition. Be very careful that you delete the Windows 2000 partition and not your Windows 98 partition! On the other hand, if the Windows 2000 partition is FAT or FAT32, you can selectively just delete the Windows 2000 files. First you will need to make the files visible. Do this by running the command:
ATTRIB -H -R -S C:*.*
The files to delete first are: BOOT.INI, NTLDR.EXE, NTDETECT.COM, ARCSETUP.EXE, ARCLDR.EXE, NTBOOTDD.SYS, and BOOTSECT.DOS. Do not be alarmed if you cannot see all these files, just delete the ones which are there. After you have done this you can remove the Windows 2000 directory. Again, ensure that you delete the Windows 2000 directory and NOT the Windows 98 directory. To delete a folder, use the DELTREE command.

If you would like instead to make Windows 98 the default operating system and leave Windows 2000 installed, then boot into Windows 2000. Right-click on ‘My Computer’ and click ‘Properties’. In the window that appears, click the ‘Advanced’ tab and click ‘Startup and Recovery’. In the next window that appears, you can select the default operating system.