This is a general purpose serial port infrared receiver. With the help of appropriate software (see below) you can control different functions of your pc from a distance. For example you can control your home cinema settings (volume, play, pause, stop etc), your winamp etc.
It uses for receiver TSOP 1738 (38 KHz) but it worked well with TSOP 1736 (36 KHz) and a remote Sony which works at 40Mhz.
The two transistors light up the led when a signal is received. Any kind of led will fit.
The software that can be used are:
# Girder + Igor Plugin
But keep in mind that each software uses different pin out. Details can be found at the schematic.