USB-Serial adapters long ago were notoriously troublesome for many MegaSquirters so we figured we'd do some research and find the best one out there for the best price.
This USB to Serial Adapter has been tested and works properly with several versions of MegaTune from 2.20 up to the latest 2.25p3, as well as all versions of TunerStudio. We've also tested on three different brands of laptops (extensive testing with an IBM Thinkpad T42, also tested with a Dell laptop and an HP Tablet PC) with the standard B&G MS-I code, multiple versions of the MS1/Extra code, and multiple versions of the MS-II and MS2/Extra code. We've used this adapter to flash the firmware back and forth between MS-I and MS1/Extra code as well as flashing the MS2 with different versions of it's code with no problems at all. I've yet to have even a single problem using this adapter under Windows XP using the driver that is installed automatically (you should be connected to the internet and allow Windows to check the internet for driver updates when you first plug the adapter in). Some versions of Vista have trouble finding the correct driver, but once the driver is installed this adapter works with Vista, too.
If you need a copy of the driver, click here . This link will load a self-installing file.