Sony Ericsson Z500

If you buy one of those cheap ones off of eBay, just MAKE SURE you download your USB drivers direct from the Sony-Ericsson website (DCU-11 USB cable). Most (not all) of the driver/software cd's that come with those cables are pretty outdated since the DCU-11 has been in use for various Ericsson phones over the last couple of years. While you're there, you may as well download the most-updated software too (Mobile Phone Monitor, Sound Editor, SynchStation, etc.).

Or better yet, go with the other guy's recommendation here about Float's Mobile Agent. If you go with Float's stuff, don't download any other Ericsson software since you won't be needing it anyway (it also causes serious conflicts with Float's software). It does everything the Ericsson software does and MORE (just do a google.com search for "float's mobile agent"). Be sure you're USB drivers are properly installed (check Device Manager for any errors), make sure your COM4 port is enabled in Phone Monitor Options (in your Control Panel folder) AND Float's Mobile Agent (Connection settings).

I have one of those USB cables for my Z500a and I can't get it to work at all on my Windows 98SE PC. Seems like a TON of people have been having problems with it too, but most of the time the problem is easily figured out due to mis-matched COM port settings.