Yamaha CRW-F1 CDR. It's used to burn audio cd's only, because the audio quality of the cd's it writes is extremely good and it writes cd's in such high quality and low speed that simply no stand alone cd player, no matter how old, will be able to read it.
For instance I own Philips CD100, I think one of the first cd players. You can burn an audio cd on any modern dvd-rw blue ray writer and the chances are very high these old players won't read them.
Oldest part I have in/on my rig is my Antec 900 case. I cant see any reason to upgrade unless GFX cards get even longer. She's a beast 2 front 120mm, top 240mm, back 120mm and side 120mm fans. Cool as ice!
Although I have a nicely working AMD Socket 754 Athlon 64 3200+ system with a Radeon 9600 and an Audigy 1, that is not my main box. The longest serving component in my main desktop is the CPU, an Athlon II X4 620, one of the original ones with the disabled L3 cache (mine has come through and had the L3 work on 3 different boards by 3 different makers). It does what I have needed it to do faithfully since release in 2009 and I expect it to continue until at least Windows 9, I have absolutely no intention of ever letting my CPU be subjected to the indignity of WinME, Vista or 8 as it runs 7 just fine.
Well built my first system 2 years ago and haven't upgraded anything. Everything was bought new. So really don't have any old components. I imagine I'll be reusing my haf x and my power supply for a long time.
Oldest parts are my DFI LanParty x48 motherboard with a Core 2 Duo E8600 overclocked to 4 GHz. Everything else has been cycled a few times (hard drives, power supply, sound card). Video cards get updated the most, about every 6 to 12 months (currently a GTX 670). Still powerful enough to play every game I've thrown at it on highest graphics settings, most recently Borderlands 2.
I'd say the oldest component in use today with my main rig is definitely the WD 320GB SATA disk, which I use to store my Virtual Machines. That's now several years old and going strong. I'll eventually replace it with a larger Hitachi disk though.
In my desktop gaming PC I built after making it out of the AGP scene, I transferred my 320Gb Seagate SATAI drive to the PCIe build of which I am still using today. In fact, I am looking at selling it soon as of recently - that along with the second oldest part, being the 500Gb Seagate SATAII drive. After that the third oldest component would be my 8800GTS (640Mb) card of which I have had to oven bake several times in the last year to get her to run just a little bit longer after the sauder joints somewhere failed at times.
But... ...now that I've come to the end of my post I've realized I guess my oldest part just may be my NEC DVD-R/W drive (PATA) that I got probably some seven years ago - I dunno - somewhere back in '05 something perhaps.
What will be my newest piece of hardware to come? An SSD of course. ...But then again why settle with my Asus P5K-E AP-Wifi motherboard running SATAII when SATAIII bandwidth specs are out there?!? ...It never ends, does it.
In use would be a 500GB Maxtor from 2000 something with 5.3 years of on time, its a redundant backup at this point in its life but still in use. The oldest part I have in my gaming PC is the Razer Sound card from a previous build. I had an old P4 630 system running until I sold it, but its still in use in his possession.