Free PC Remote Control Software
There is some excellent free remote control software out there at the moment. The software tends to be free for home or domestic use, but you'll need to pay something for commercial usage.
My personal favourites do no require you to open up any ports on your firewall, you just have to download and install the free client.
Team Viewer is one such program. Your colleage can install the "instant support" tool for free, and then they let you know the 9 digit machine ID, plus the four digit password. You can then run the client/host version of the client, also free from their site, and type that information in. You'll gain install access to their machine, including file transfer, recording sessions and copy and paste.
RealVNC require you to open a port on the firewall, but works great with VPNs or if you port forward on. It's free, and has a host, client and client/host edition. All are free for personal use.
Zolved is another free session based program that you download from a website. You run the program, inform your colleague the details and shar your screen. It has a look of the free WinVNC, but with the install method of Team Viewer. Recommended when your normal method fails.