I'm pretty sure DOS 6.22 can only access a maximum of 2 gigs per drive, with fat or fat16. However I know of a few ways to kinda work around this.
OK from my point of view you have two options the easy way and the hard way. I recommend the easy way.
Easy way: Install DOS Box.
Heres the Website
Hard way: Create two partitions on your hard drive. One 8 gigs the other the rest of your disk. Make the 8 gigs one use the file system fat32 and the other NTFS. Install Windows 98 SE on the 8 gig one. Once you have done that install any dos sound card or mouse drivers ect. Then go c:\ and find the msdos.sys file. Right click go properties and uncheck read only. Open it up with notepad and set Boot GUI (or something similar to that) to 1 if its 0 and 0 if its 1. Go to C:\windows and copy the win.com file to C:\. On the net you can probably find a freeware program that allows 98 to read NTFS partitions so look around. (A quick google found me
this) Once you have done that reboot you will now be in DOS with an 8 gig drive that is readable. Alas you can't access you NTFS partition in DOS. To do that go to C:\ and type 'win' without the quotes.It should boot into 98 SE where (with the program you installed) you have a GUI interface that allows you to read the NTFS drive and the DOS one.
Install Windows 2000 as you normally would but
dont delete any partitions (thats why you partitioned it before you installed any thing). I dont have any expierence with windows 2000 but it
Should come up with a menu when you boot up to choose either 98 SE or 2000.
I'm pretty sure you can edit the boot.ini file (located in the root of the NTFS drive) and rename Windows 98 SE to DOS 7.1 but make a
backup first! But again I have no experience with 2000.
Note: This can probably be done with 95 or 98 or maybe even ME. I have some doubts with ME and 95 though.
Now that has to be my longest post ever! Well not quite.