I needed to do some work using a pin pad (a device that allows you to enter a numeric code at a point-of-sale or other system) and needed to test it in a 32bit Windows environment. The pin pad uses a serial port to communicate to a computer. Of course no portable computers (maybe no desktops either, it's been years since I've had one) have serial ports anymore, so you have to use a USB to Serial adapter. It seems like many brands of these converters use a chip by a company called Prolific. Prolific makes the chip that lives in the converter that does the translation from serial to USB and back. I found the drivers from prolific and the device loaded just fine on Windows 7. I then created a Windows XP image in VMWare.
This is where the fun started.
I loaded the driver in Windows XP but no matter what I tried I couldn't get VMWare to take control of the adapter. Every time I chose Virtual Machine -> Removable Devices -> Prolific USB device -> Connect it would give me an error: "Driver error". Nice and specific and helpful right? I rebooted the host and the guest, tried without the driver installed on the host and rebooted again. Try as I might nothing worked.
Long story short, I was plugging the adapter into a USB3 port and either VMWare or the driver didn't like USB3. So If you are seeing a similar problem, try and find out what kind of USB port it is. I was using Windows 7 on a Lenovo W510. This machine has USB2 and USB3 ports. The 2 obvious USB ports on the left hand side are USB3. There is a USB2 port on the back, but I keep another device plugged into that one so I didn't even think to try it. It turns out though that the W510 has dual ESATA/USB2 port next to the USB3 ports. That dual port looks physically different than a normal USB port so I assumed it was just ESATA. I plugged the usb to serial adapter into this dual port and everything worked flawlessly.
Hopefully that will helps someone save a bunch of time that I wasted trying to get it to work.