It's been so long I really can't recall anymore. (Edit: but just like you, I do remember that I had the ICQ window visible at pretty much all times, and I could comfortably fit an Emacs window, the contact window a chat window on my desktop's 1024x768 screen.)

That being said, the window in that screenshot is about 200 x 320 px. It would have taken about a third of the horizontal space of the screen, and about 2/3rds of the vertical space of a 640x480 screen. It was certainly usable -- way, way more usable than Skype on a full HD monitor today -- but lots of stuff was claustrophobic in 640x480.

(Then again, most modern apps are practically unusable if you resize their window to 640x480...)