Because the original digital versions were recently delisted from major storefronts like Steam and GOG by Epic Games, finding a "buy" button is now difficult. However, there are still reliable ways to get the game:
: If you want the game to look sharper, look for the HD Texture Packs (like S3TC) also hosted on OldUnreal or ModDB. System Requirements (1998 vs. Now) Download Unreal PC Game 1998
: You can often find original CD-ROMs or "Unreal Gold" editions on eBay or Amazon. Because the original digital versions were recently delisted
: Community-run preservation sites like the Unreal Archive host patches and files for the game, as it has largely entered the realm of "abandonware" in the eyes of the community. Now) : You can often find original CD-ROMs
: You can find legitimate disc images (ISOs) of the 1998 original for preservation purposes at the Internet Archive. Essential Community Patches