Welcome to the forums! Just a couple of questions about this:
Have you tried plugging device directly to another USB port?
When you open up the GPSInfo program, do you see any com port in the COM Port field? If not, please close the program. Right-click on its icon > select Properties > go to the Compatibility tab. Check the box that states run this program as an administrator. Click Apply and OK. Then, open up the GPSInfo program and choose the proper com port.
Do you have any antivirus program running in the background? If so, please disable it and restart your computer?
Once it restarted, go to your Device Manager. Then, right-click on Computer > Manage > Computer Management > System Tools > Device Manager > Ports (COM & LPT) > Prolific to USB Serial Comm Port (COMXX). Did it have a yellow error exclamation point besides Prolific?
If so, you need to uninstall the driver. Go to Control Panel > Programs. Scroll down the list of the programs and look for PL2303 USB-to-Serial. Highlight the said program and click Uninstall. Once the driver is removed, turn off your computer and wait for a few minutes. Power up your computer and download the latest version of the driver from here: (http://www.usglobalsat.com/store/download/62/windows_pl2303_usb_driver.zip
). Make sure to extract the file first before installing the driver.
Let me know how it goes.