I use PCAnywhere at work to 'take control' of remote servers. It also has a file transfer facility and the ability to copy the clipboard of one machine to another. You have a small 'host' programs that runs in the background on the machine you want share that listens for incoming connections. It also comes with security to stop unauthorised access. You have to install PCAnywhere on the machine you want to access the remote computer with too.
Windows Netmeeting can do a similar job. It does have a file transfer facility, but I haven't used it so I can't really comment on how good it is. The big bonus is that it is free and comes with windows, although Microsoft have 'hidden' it in later versions of Windows. To set it up, go to Start|Run and enter conf. This will install it. Then you have to set up Remote Desktop Sharing. The advantage is that everyone has NetMeeting whether they realise it or not.