Passively converting from PS/2 to USB or USB to PS/2 is only possible with mice and keyboards that are compatible with both PS/2 and USB connections. The following are two ways to determine if these products will work for you:
Look on the bottom of your mouse or keyboard for a PS/2 symbol or picture, and a USB symbol or picture.
Your mouse or keyboard came with a similar PS/2 to USB or USB to PS/2 adapter.
You can use the USBPS2PC to actively convert PS/2 keyboards and mice to USB.
Note: StarTech.com PS/2 adapters are only officially supported by mice and keyboards.