No need to lock.....
THere are a LOT of free demo versions of games.
Personally, I've found that 90% of the games have more than enough on the demo to satisfy my gaming...
There's only a few games that I thought... "wow, I beat levels 1,2,3. I really need to go out and buy the software now to beat 4-40."
Plus, sometimes you may even score the chance to be on a beta testing team or something... THEN, you get the game in advance of its release and just have to play it for a while and report back any bugs.
It's been a long long time since I've downloaded many demos... but if I recall correctly,
www.happypuppy.com,
www.gamesdomain.com are two places that I remember. I'm too lazy to link for you though. Sorry.