I suspect you're thinking of upstairs in the Golden computer arcade in ShamShuiPo. It's still there, but it was already "cleaned up" and respectable when I went back in 1999, having shifted focus almost entirely to business needs. I went back again a few years ago, and maybe it's just because I'm older or maybe it's because I've discovered HQB in Shenzhen, but it feels really boring now. You can at least still find the latest half-a-billion-in-one NES emulators downstairs, so that's always a good thing.

When I went in 1992, it was crazy. CDs didn't have much adoption for computers by then, so the market was still floppies - IIRC HK$10 per disk and another HK$10 for a photocopied manual. They'd take your money and phone up some guy and tell them the four digit code and 10 minutes later someone would hand you a stack of disks. It felt weird that it was so blatant, but the first time I went by myself, I couldn't find it and asked a policeman for directions. He said in English, "Oh, the copied stuff? Over there!" and pointed to it!

That said, I only ever bought 3 disks from there - partly because I didn't have much money, but mostly because I found the programming books downstairs even more interesting. They were translations of all the English programming books, for about HK$30 each. The text may have been all Chinese, but the source code wasn't, so I bought a couple of books just for the diagrams and the source code.

I remember heading to HK on a high school trip and we all ended up in that building, many people grabbing loads of CDs. Felt like Christmas! (I was too worried about customs in my home country checking my bags on arrival though!)

I was a permanent resident there in the '90s, and this was a piece of nostalgia I didn't expect to stumble across today.