I posted a response somewhere here a couple days ago and mentioned that I use a USB-Serial adapter on my laptop. Since then I have received 4 emails asking for more info, and I just noticed another post asking about the same issue. I'm posting here to help everyone else, and to reduce the emails I receive.
I have a Toshiba laptop that has no serial ports, but it does have 3 USB ports. I'm running Windows XP.
I purchased an IOGear model UC232A. I have a friend who bought a USBgear adapter and never got it to work on his WinXP box. He ended up buying an IOGear one.
When I got the adapter from my local computer store, IOGear didn't have an 'XP-compatible' driver, but after emailing them, they said the Win200 driver can be used on WinXP - the only 'issue' with it is that Micro$oft hasn't tested it themselves I have had no problems with the driver.
I've used this adapter on a Magellan ColorTrak, Garmin GPS III+ and a GPS V with only one problem. Older versions of MapSource only supported serial ports up to COM4. When plugging in the USB-Serial adapter, I was getting COM6. A little research found that the COM port you get is dependent on which USB port is used. My 3 USB ports yielded COM4, COM5 or COM6, so using the right USB port fixed the problem. The most recent version of MapSource supports up to COM8.
I hope all this helps someone out there.
Happy Geocaching.
Lil Devil