About 2-3 hours fabricating, if you have any skill at all, and additional time to set up either [Winlirc (free) + AutoHotkey (free)] or Girder (buy). Setup time is as long as the number of functions you want to run.
http://lnx.manoweb.com/lirc/ This page pretty much holds your hand through the fab of the IR reciever, which will gather IR signals from any IR remote...like my posts, this page is verbose, full of detail, but probably could be a lot, lot shorter. After this, all you would need is the software if you wanted to just control your computer from an IR remote. All the parts are available at RadioShack.
http://www.lirc.org/transmitters.html Here is the transmitter. You need a transmitter if you want to use your computer to send remote signals to other devices.
http://winlirc.sourceforge.net/ This is WinLIRC, the program that translates the signals collected from the IR receiver to digital code that can be stored on the computer and used later. It watches the ports the receiver is hooked up to, and records whatever it sees. This is the "learning" part of your new learning remote control system. See the winLIRC home page for usage instructions.
http://www.autohotkey.com/ This program simply watches for certain things to happen on the PC, and triggers scripted events that you specify. You can use it to watch for digital code from WinLIRC, and then mimmick keyboard keypress sequences and mouse movement based on the IR codes it sees. You can use Autohotkey to translate keypresses, button presses in your favorite front end, or codes from a Hitatchi remote into codes a JVC device understands. You can then tell Autohotkey to send that remote signal to, for example, your touchscreen monitor, or to a remote audio device, or to your VCR to tell it to record, etc. You could write an autohotkey script to send a remote code that turns on a surround sound amplifier and dims the lights whenever you start your favorite DVD software. If you have autorun enabled, you can make these things happen upon DVD insertion. You can tell it to write "War and Peace" in a word document and store it in the recycle bin whenever you press "page up" on your cable box remote, if you want. You can even use it to replace all instances of "Dwight Schrute" with "diapers" whenever you type it.