tightvnc or rdp. If they can't be arsed to install/configure one of those 2 things then I cba to assist them. Hell rdp comes with most versions of xp/vista and its got better polling/compression than most vnc solutions.
Only problem with RDP is it logs the end-user out, and you have to get their login credentials.
Most users will fork that information over, but in almost every situation I refuse to ask for that information unless its absolutely necessary for security, comfort, and more importantly, liability reasons.
You get one of those idiots out there who are sue happy, you fix their stuff, they get their bank account ripped off by some trojan after you've serviced their computer, they blame you claiming you had their information because their dumbass uses the same user/password for their banking information.
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