none. I replaced nearly everything when I graduated college in 2003.
the oldest electronics I have that I'm still using would probably be my iPod 2g (2002... it's my bathroom/shower music source), one of my monitors (19", bought in 2003... it sucks compared to any modern screen, but it gets the job done as my second monitor), and my case (2005 - Antec P180, actually looking to replace it now)