A couple things to try and diagnose the problem.
You said your computer is old, run a dxdiag and post the top third of it here, up to AND INCLUDING <SOUND DEVICES> <--- it will look like that. If your computer is too old and slow to load up graphics it can time out and you will lose connection. With the dxdiag, tell us what settings your trying to run in the game, under "video settings" when the game first loads up, whats the "texture size"? In the game, home much eye candy are you trying to run?
Connection issue could be your internet too. I know you drive truck, are you trying to connect on a wireless connection? Wireless is the worst, right up there with satellite. Even dial-up is far better than those two. To check your connection, download and install "pingplotter"(
http://www.pingplotter.com/downloads/pngplt_1.exe ) Once installed, type this address 206.16.60.41 into the box at the top left and run the ping for 10 minutes letting it ping every few seconds. Take a screen shot (hit print screen on keyboard) and open it with windows paint. Save the picture and post it here. What your looking for is everything in the green. If you have stuff showing red your connection stinks.
With that info, we might be able to help you tweak things to get it running better. I have tomorrow free and hope to be flying by 2 pm eastern. Maybe we can hook up.