I've just posted a rather long-winded message on your other thread, on the assumption that you have succeeded or will succeed in installing the 2nd copy. So ignore that post.
You're right, you don't want to install again to the G drive.
I don't know why your D drive is not available for installation. Is it not even shown on the list of partitions, or is it shown, but when you select it, w2k Setup tells you you can't do it, or some error message?
Since your copy of w2k is on a G drive, it suggests that you may have a rather complicated partition system, but I don't know.
Your idea of having 2 copies of w2k is actually a good idea. But if there's a problem installing it, then bad luck.
If that problem cannot be resolved, and you want to remove the boot option for W2k Setup, here's what you do.
These instructions are on the assumption that there's only one active partition (the partition the computer boots from), which is your C drive. If you have a different configuration, please post back.
Start computer and select the proper w2k copy from the selection screen.
First make sure that your default OS is w2k proper, and not the setup (this should be shown on the boot selection screen when you boot up the computer).
But check it anyway. When you're in w2k, right click My Computer, select Properties, Startup and Recovery.
Under the section default operating system, see if it shows the default OS as "Microsoft Windows 2000 Professional" /fastdetect. If so, leave it alone.
If not, click the drop down list and select it. Click OK to exit.
Now go to your C drive. See if you can find the file boot.ini
If not, click Tools, Folder Options, view tab. (1) Tick "Show all hidden files and folders". (2) Untick "Hide file extensions for all known file types". (3) Untick "Hide protected operating system files". click OK.
Double click the file C:\boot.ini to open it in Notepad.
First check that the line in the file that begins with default= reads:
If it's like that, it means you have successfully changed the default OS back to w2k proper, and not the Setup.
Then look under the section [operating systems]. One of the lines should be (ought to be the second line from your description):
C:\$WINNT$.~BT\BOOTSECT.DAT="Microsoft Windows 2000 Setup"
Delete that line.
This is the only change you need to make.
Save the changes and exit Notepad. Restart the computer and you should boot straight into w2k, without the OS selction screen.
When back in w2k, go back to the C drive and find the folder $WINNT$.~BT
Delete the entire folder. This is the temporary installation folder from which w2k Setup boots, and which, had the installation been successful, would have been removed by Setup. You can delete the folder now, since you're not proceeding with the installation.
This will clean your computer of the remnants of the aborted installation.
But as I said, your computer configuration may be different (for example, if your active partition is your G drive, then the instructions need to be corrected).
There may also be a way of overcoming your installation problem.