People use windowblinds to create that effect and sure it looks cool, but on a slower machine or a video card with "not as high" refresh rate, you will see some jerkiness when poping up the "start" menu and others.
 
I tried it and it slows down my machine a lot. so forget it.

There is also a little tsr called Transparent. Try www.pobox.com/~jayguerette/transparent.

Propably the easiest way to turn your windows transparent would be this little proggy... http://x.wonder.ca/stevex/nthack/transx.zip

There is also this WINFX desktop tweaking software at www.stardock.com

I to have seen this transparency and it wasent from any of those programs. I saw that some beta builds havd it and I to was wondering how to make this work in win2000 without extra programs

Widnows 2000 includes support for transparent windows and menus. It was supposed to be included in the final version, but it was causing too many problems, so they didn't implement it. (this one of the reported 65,000 bugs, even though it isn't a bug!!!!)
 
so the only way to get it now, is through other programs that make use of the alpha blending that is built in to 2000. Microsoft intentionally left the stand alone option to do it out. So if it cuases problems, then it is not Microsoft's fault, it is the makers of the other software.
 
What you saw were probably pics of some developer's beta build when they were still working on getting the bugs out of the transparency code.
 
BlaZeR2

Great !!!!