Just so you all know right now, No, this is not a hoax... if it was a hoax I would not have just spent the last hour talking Tara's mom through the removal process... nor would I be posting it (ask around... I don't send hoaxes). So if you are a MSN Instant Messenger user, I HIGHLY suggest you read up on this...
TAKEN FROM http://virus.com/article/index.php?article=943 (includes removal instructions)

Name: W32/Choke
Aliases: I-Worm.Choke, Win32.Choke, W32/Choke.Worm
Type: Win32 worm
Comments: W32/Choke is a worm which attempts to send itself through the MSN Messenger instant messaging program.
The worm can send itself through MSN Messenger using a variety of filenames, including ShootPresidentBUSH.exe and Choke.exe.
It copies itself to c:\choke.exe and sets a Registry key HKCU\Software\Microsoft\Windows \CurrentVersion\Run\Choke
in order to run automatically when Windows is started.
When first executed the worm displays two dialog boxes. The first dialog box says:
"This program needs Flash 6.5 to run!"
The second displays the message:
"Cannot run program!, Quitting"
The worm creates a file called about.txt in the root of the C: drive which contains the following text:
Choke , Copyright ® 1886 ... A MAD CHRISTIAN --------------------------------------- Go talk swearwords about God You all will die, stupid humans. You fools didn't see what you have done Bye slut, go talk shit about me. (Call me a 'psychophatt', but I respect the Creator of life...) ' Consider your earth '

¤?X?X?X?X?X? says:
Hey Scott. It's Mom. How's it going?
¤?X?X?X?X?X? says:
"President bush shooter is game that allows you to shoot Bush balzz" hahaha (this will be in a different font from the person you are chatting with, showing that they did not type it, and it is infact the virus "talking")
¤?X?X?X?X?X? would like to send you the file "ShootPresidentBUSH.exe" (41 Kb). Transfer time is less than 1 minute with a 28.8 modem. Do you want to Accept (Alt+T) or Decline (Alt+D) the invitation?
¤?X?X?X?X?X? says:
;)
Scott-NightStorm-]\[][G}{T§TÖ®]v[ says:
not too bad... just about to go get food
¤?X?X?X?X?X? says:
;)
You have declined to receive file "ShootPresidentBUSH.exe".
¤?X?X?X?X?X? would like to send you the file "choke.exe" (41 Kb). Transfer time is less than 1 minute with a 28.8 modem. Do you want to Accept (Alt+T) or Decline (Alt+D) the invitation?
¤?X?X?X?X?X? says:
;)
The person you are talking to will wink ( shown as ;)... that's a wink) everytime you are showing as typing, so this is a pretty good clue in itself that they are infected, and I suggest you send them to the site listed above immediately, because they will no know they are infected unless you tell them (they are totally unaware that any of this is happening). Another hint is that when the ;) are scrolling, the info bar at the bottom of the window will show "President George W. Bush" as typing... so PLEASE watch carefully for this... and I hope none of you ever have your computers infected by it.