Max Size for Registry File

What is the purpose for this setting in the Virtual Memory settings on a Win 2K Server?
If you set it too low, you are prompted to increase the size, and asked if you want to. If you answer no, it increases the registry file size anyway.
I’m currently in school and none of my classmates, nor my instructor know what it is for. After a simple search, all I could find was recommended settings(the defaults, apparently), but no real reason as to why it would be changed, or why it is there in thefirst place.
Any help on the matter would be greatly appreciated.

You can email me at thatmagicguy@hotmail.com if you feel like it.

Thanks,
Patrick