If by any chance you felt the same enthousiasm I felt when re-reviewing the Dungeons & Dragons basic set... you may have sighed. Where can I get those rules? On an Indian reservation in Nevada? In the Library of Congress? Where?
Or you may have thought, that the guys at Osric shouldn't have taken the Advanced rules to redo, but these instead. Right they should! No worries. Someone did the same trick as OSRIC for D&D. At least two someones.
Labyrinth Lord by Daniel Proctor (et al) is a 90% rewrite of the basic D&D set. Some things have different names, some rules are slightly different. But it's basically... basic! You can download the newest version without art for free, or shell out a few dollars for one with art - or even a print. Or you could get it in german.
Basic Fantasy by Chris Gonnerman (et al) is more somewhere in between basic D&D and AD&D. But there are also more free supplements for the game - adventures, monster books, sheets, Italian stuff. And just like LL, you can download the rules themselves for free too.
Now I wonder... would all this nostalgia be enough to actually play the old games again? Or try them for the first time ever? I gaze with amazement. Even if my memories are full of joy. For me I'm still not sure. But for many the answer is a simple resounding yes.
Update: WOTC have realized there is a market for old D&D by now, and you can get the B/X D&D sets on DriveThru in pdf form.