You mean the text-to-speech thing on XP?

Man, that thing's hilarious!

I wanted it on my Windows Me comp so I dl'd CoolSpeech. It was fun, but I only had the trial version.

Find out more here: http://www.bytecool.com/voices.htm

There are quite a few different voices available (I'm not sure if they work with the XP text-to-speech)

There's also: http://www.nextup.com/TextAloud/SpeechEngine/voices.html

Oh, I also found this which might be interesting:

Microsoft does not provide additional speech engines (voices), but a number of third-party products are available that support the new Microsoft Speech API. For information on these products, visit the following Microsoft Web site:
http://www.microsoft.com/speech/evaluation/thirdparty/engines.asp

Good Luck Simon! I'll post more if I find anything else

In the meantime wrap some aluminium foil around your head to stop the messages being beamed into your brain  

Don't you mean foil boxer shorts?

Have you tried "MS Reader", Simon?

http://www.microsoft.com/reader/downloads/pc.asp