Folder limits on NT4

Folder size in general? Really can't do it without a third party product like Quota Manager (http://www.ntpsoftware.com/products/qm/default.asp)

If you want to limit the size of user profiles and have SP4 or higher, see here:

http://support.microsoft.com/support/kb/articles/q185/5/61.asp

If you want to limit how much users can store in their personal folders, another approach is to put all personal folders on a dedicated partition. This doesn't limit individual users but does set up a limit on how much all users can save.

Sp 5 cd has a set of utilities like QUOTA manager, which allows you to limit the profile size, the desktop size, the Internet cache size, not exchange.
Under exchange you need to limit the user's mailbox to a number of messages or a size.
You mustdo it "User by user", That's Microsoft
way of doing things !!!