Unfortunately, I'm unaware of how to do this natively but I recommend using Dummynet which has a Windows port of the FreeBSD networking tool. Oddly, their website appears to be down so here is the Google cache:

http://webcache.googleusercontent.com/search?q=cache:YJ8bhlD...

You need to install the drivers but once done you effectively use the same commands with ipfw as on FreeBSD (as described in another thread http://news.ycombinator.com/item?id=2005190). I just used it for the first time the other day to test a web app browsing with a 400ms delay on a WinXP machine. It worked like a charm.