Teamviewer has saved my butt several times over the last few years. The application allows for easy non-persistant remote access that the client can control. The supporter and the client both run the same application located at http://www.teamviewer.com. There will be two sets of numbers. One will be a session ID that the other person will input as well as a password. These numbers change everytime.
The application is free for non-commercial usage like remote controling your Mom’s PC to remove that conficker virus (again!)