How I can get my friends ET working on Windows Vista??

Rightcklick on the ET.exe and choose a compatibility mode (Win XP).
Sorry, I don't use Vista.

I have vista and ET works. Just instal that. Thats so easy

Yes just install it than use right click and run et as admin. Thats the clue. SECURITY? dunno
Stepf

Just remove all , INSTALL ET.
Then install patch 2.60.
Go to pb map click on PBWEB then go update punkbuster.
Then download 2.60b version and remove 'ET" and old 'ETDED'
And copy the both of 2.60b in Enemy Territory map.
Then open ET with adminitrator .(Right click open as administrator)
Let know of it works,<-=

Grtz Shark

They Will Never have smooth game play with vista only newer games like Cod4 etc will get the true feel. Even On Great Spec There still laggy.

Since W:ET is from 2003 it has Problems with Multicore CPUs. When you get Problems running W:ET on a Multicire CPU you should assign it to run only on a single core:
open the task manager
right click the ET.exe process
and then set the affinity to one core

piece of cake, click icon right click, go properties compatabilty run xp pack 2 and also always run as administarator, works for me, let me know..

A little tip: Vista doesn't like you hacking too much around program files, a good idea is to install it somewhere else
My ET runs best (least error messages and disconnects) in 800x600 and with ET Starter Pro (a launcher), which makes me able to switch between other versions
(On Vista btw)