Control LED using usb to parallel converter
I have never seen a gadget that claims to be a real usb-to-parallel converter. I have seen usb-to-printer-port converters, but they do just that: create a windows virtual printer port. 

The difference between usb-to-printer converters and usb-to-serial converters is not so much the converter itself, but the (sad) fact that windows software often seems to use the windows serial port interface, so a usb-to-serial converter can sneak beneath that interface and preent itself to the unnkowing program as a serial port. 

AFAIK there is no compareable windows parallel port interface, so windows programs use either the windows printer interface (which is at the level of print this file using this printer driver) or use the parallel port hardware directly. It is probably not totally impossible to emulate the parallel port in hardware, but I have not seen a product that does so. (but check AndrejanKo's comment)

So for the hardware hacker an usb-to-serial converter can be almost as usefull as a real serial port, but an usb-to-parallel converter (which should be called usb-to-printer converter) is almost useless.