...and still do! :)
Just all those little computer things that used to fascinate you. For me the main two are:
The old Windows 95/98/ME Defrag program, with all the squares that would change colors. I used to sit and watch it for hours while it defragged. Windows XP (and I'm assuming Vista and 7) now just have a little bar at the bottom...nowhere near as interesting! :-)
And then we had an old Enya screensaver that played the music video to "Only Time". I used to sit and watch/listen to that for long periods of time.
Also Need for Speed: Porsche Unleashed. The. Best. Racing. Game. Ever. Just sayin' ;-)
And pulling the little silver slide on floppies, and making it slap back into place. Apparently Sony is going to stop making floppies in 2011, I bet my kids (I'm only 16 now) will never understand what the "Save" symbol actually is! Sad day...
Also opening those old cd cases that had the same silver slide thing. You opened them with two tabs on either side. Anyone else ever used those?
So yeah, just any little things that you have fond memories about on old computers :-)

The program Defraggler has all those squares while it operates. It's also much more efficient than the current Windows defrag.
One of my memories:
My first strategy game was Close Combat: A Bridge Too Far and I loved it so much that I downloaded the Close Combat Windows theme, so whenever there was error there would be a little explosion and stuff. I also loved that starfield screensaver.

The big game boxes. There's just something so much more satisfying about them.

Pirating / downloading games. I stopped doing that few years ago.

As a kid, I remember browsing through Swimsuit Illustrated, when Google was yet to be (back then search engines like Altavista and AskJeeves dominated) and dial-up wasn't all the rage yet. Good times.
Yeah I remember those, I threw the last one away about 7 years ago. I liked those CD cases tbh, very stylish and solidly made, unlike the cheap padded ones with rough sleeves that can scratch the CDs, that are being sold these days. There wasn't even a need for a zip to close them, you could close them with a resounding "thwock". Nostalgic times.

Big boxes scare me. I still have nightmares about installing programs that required over 20 floppy disks.
abort, retry, fail?
AAAAAAAAAAAAAAAAAAAAAHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ah, defrag is still a very nice thing to see. Me love does not get what I see in all those blinking little boxes that change places. Both with defrag and old games, that is. ^^

Street Fighting Man
-Getting it home and bashing people over the head with a crowbar.
QBasic
-Trying to get the games to play for it was a pain but fun.
Sopwith
-Printing out the source code and trying to figure it out.
Big boxes
-Chopping them up and mounting them like trophy bucks on my wall.
Duke Nukem 3D
-My friend had just got a new computer. He came pounding on my window in the middle of the night. We were up till 6 or 7 am playing it. I was jaw dropped and awe struck.
ID Anthology
-I bought it and the Egghead Software guy said, "That's the only way your able to buy Quake." It was sold out everywhere. I bought it because I wanted DOOM. I only had the sharware copy.
Egghead Software
-I miss it so much.
Quake
-The first time I played it. It was so awesome. That night when I was going to sleep my radio started playing Funeral March song. I started laughing. Maybe that was the end of gaming?
Here it is: http://www.youtube.com/watch?v=umgty3qGCcY

The first time I ever played Thief, when my friend got it when it came out.. He liked it but he sucked at it and was too used to run and gun games, so he gave it to me. I remember spending hours at his house while we would take turns after high school trying to break Cutty out of prison, and figure out the best way to do the missions.
When I got the CD to take home, I managed to beat it after many weeks. Been a huge fan of Thief ever since.

You mean a caddy? Not a CD case as such, it was used in early CD-ROM drives to keep the CD stable during reading.
Did anyone else have the screensaver with the castaway on the desert island? Man, you could sit and just stare at that thing for hours, wondering what he'd do next :-)

Reading 100+ page thick game manuals and getting those big poster tech charts with my latest RTS.

Yes, with a big cheesy grin. :) Reminded me of watching Battle Chess.

CD Caddy (http://gbennett.whsites.net/zencart/images/products/M2705.jpg) ?
For me, the biggie is explaining to my nephew how my games used to come on tape and he's like "what's tape?"

Agreed.

Playing WWF attitude as a kid.
continuously playing the "don't p*ss me off!" sound clip
*tap* *tap *tap* *tap*