Hi Johnnyi,
That answer comes out as a Yes and a No.
Yes circumstances.
iChat users at both ends.
Jabber Buddy list.
This is basically an iChat to iChat connection and the Buddy list you started from does not matter. It starts up the A/V side of iChat
No Circumstances.
iChat has three Buddy lists (AIM, Jabber and Bonjour for Mac to Mac at the same LAN location such as your house)
Adding MSN or other IM names (Yahoo or similar) has to be done on the Jabber Buddy list - which means you have to get a Jabber name and arrange this to be with a server that does Transports. Although the Jabber.org people are working on Video and Audio codecs of their own they do not work with the ones iChat uses.
This means that you can only use the transport enabled connection to Text chat.
Options for Video from a Mac to a PC using MSN
aMSN or Mecury Messenger (No Sound )
See 11 sand 12 here
http://www.ralphjohnsuk.dsl.pipex.com/page5.html#_other
The earlier numbers of the list on this part of page 5 lists other apps that will text chat to MSN users as they can join multiple IM service (AdiumX is one)
Some options listed are apps that work on both platforms and have their own codec/ways of doing Video or Audio chats (Again these can not join iChat or MSN they are stand-alones in that respect)
EDIT:
I see others have made similar suggestions to my last paragraph
7:59 PM Friday; July 6, 2007