The abandonware scene is a great source of classic games, but be aware that there is a limit to what you can play on a modern system. Windows XP has compatibility modes, available through the program properties, but they often don't work. Read the guides on these sites and do your best, but some of these games will simply not work on modern PCs.
Even with that limitation, it is wonderful to see that Zork still has its appeal and that Might and Magic 4 really was as revolutionary as I thought when I was 13. These games are what made a lot of us into gamers, and their replay value will never die.
Have fun and keep gaming!