quite easy! I've done this on school millions of times! But I have a dutch version of Win2k. But anyway this is how I do it. Right-click on My Computer.
Your now in system properties.
Go to Advanced and than click the up-most button (it's called prestations here with me) Then you get this menu pop-up with Virtual memory! Or paging size, than you click [change...]. Okay I'll explain the menu from top to bottom.
On the top you can change the drive from which you want to draw the amount of MB's from, it would be wise to take the one with the most rpm and most size. After that you can change in number boxes the amount of size you wish to take. Mine is 384 MB's to 768 MB's besides those number boxes there is another configuration button, that's for input. And far below you can change the registry-size. It's a very good menu believe me, it's just located on a spot where you don't look very fast.
Like in Win98 there its also in the system config, but somewhere below in advanced if I recall correctly. also called prestations or something. I don't know the word in english ^-^'