One of the major stumbling blocks to playing D&D online using the old books is that they are all out of print and, therefore, not everyone has access to them. I have because I am a collector at heart and don't mind scouring Ebay and other sites, looking for another piece of memorabilia to add to my collection. However, I cannot demand the same from my players in order to play the game. Playing face to face is easier in that we would only need one copy of the books to pass them along, but online it's another story. I also cannot encourage my players to seek out scans or pdf files of these books and download them. This would be tantamount to piracy. However, another solution presents itself: the retro-clones.
Retro-clones are rule systems that try to emulate the feeling and play style of the old school D&D and AD&D. They were made possible when WotC published their Open Gaming License (OGL), which allowed many third-party publishers to modify, copy and redistribute many of the original rules. This led to the creation of several retro-clone systems from 2000 to this day. I have checked a few and some are even available online for free from their respective publishers. This post is not about all the retro-clones that exist but only the ones that caught my eye.
Using a retro-clone system would effectively allow us to continue playing our game as before even if not everyone has access to out of print material. That's why the retro-clones exist: so that current gamers can experience old school play style, not being forced to pay sometimes exhorbitant prices for the old books. I have come to appreciate Labyrinth Lord from Goblinoid Games. Already there are two books published for this line: the first emulates the B/X sets and the second allows to play AD&D 1st ed. style. I've checked them, they're quite good and 100% compatible with the old modules with no conversions required. Another option is OSRIC which is a considerably larger book, also available for free, that emulares AD&D 1st ed.
At this point, I think this is the way to go. As I said, I could not demand from my players the same willingness to go out and buy the old books when something free is available online that allows the same play experience. This is the next best thing. I'll continue to expand my collection which already includes the likes of Keep on the Borderlands and Temple of Elemental Evil so we have no shortage of adventures to play in the near future.