well here you will find good commerical games which
are released as freeware now.
some of them are ad supported.
(i havent tested all the ad supported versions but
for what i have heard the ads are NOT ANNOYING.
cause they appear in pause menus.

ad supported games:
psi ops
the suffering
full spectrum warrior
area 51
rise and fall

for more games visit the
[url=http://en.wikipedia.org/wiki/List_of_commercial_games_released_as_freeware]Wikipedia Entry[/url]

well here you will find good commerical games which
are released as freeware now.
some of them are ad supported.
(i havent tested all the ad supported versions but
for what i have heard the ads are NOT ANNOYING.
cause they appear in pause menus.

ad supported games:
psi ops
the suffering
full spectrum warrior
area 51
rise and fall

for more games visit the
[url=http://en.wikipedia.org/wiki/List_of_commercial_games_released_as_freeware]Wikipedia Entry[/url]

Notice:
According to JP_Russell
Psi Ops, The Suffering, Rise And Fall, and Area51 contains Starforce.

So use at you own risk.

Psi Ops
(brutal 3rd person telekenesis action)
2,5 GB
User Score: 8.6
[url=http://www.fileplanet.com/187537/180000/fileinfo/Psi-Ops:-The-Mindgate-Conspiracy-(Free-Game)]Download Site[/url]
[url=http://www.gamespot.com/xbox/action/psiops/index.html?tag=result;title;2]Review[/url]




The Suffering
(brutal 3rd person horror action)
1,2 GB
User Score: 8.2
[url=http://www.gamershell.com/download_33314.shtml]Download Site[/url]
[url=http://www.gamespot.com/pc/action/thesuffering/index.html?tag=result;title;0]Review[/url]




Full Spectrum Warrior
(tactic action)
1,6 GB
User Score: 8.2
[url=http://www.gamershell.com/download_33784.shtml]Download Site[/url]
[url=http://www.gamespot.com/pc/strategy/fullspectrumwarrior/index.html?tag=result;title;0]Review[/url]




Area 51
(FPS)
2 GB
User Score: 7.5
[url=http://www.gamershell.com/download_33790.shtml]Download Site[/url]
[url=http://www.gamespot.com/pc/action/area51pc/index.html?tag=result;title;0]Review[/url]




Rise And Fall
(RTS)
2 GB
User Score: 8.0
[url=http://www.gamershell.com/download_33916.shtml]Download Site[/url]
[url=http://www.gamespot.com/pc/strategy/risefallcivilizationsatwar/index.html?tag=result;title;0]Review[/url]

Gore Special Edition
(FPS)
0,5 GB
User Score: 6.0
[url=http://www.4drulers.com/gore/index.php]Download Site[/url]
[url=http://www.gamespot.com/pc/action/goreultimatesoldier/index.html?tag=result;title;0]Review[/url]

S.W.I.N.E.
(RTS)
0,7 GB
User Score: 8.1
[url=http://www.stormregion.com/index.php?sid=422ce1c53b6f820062ee1aa9ba22bd1b&activeMenuID=swine&activeProjectID=103]Download Site[/url]
[url=http://www.gamespot.com/pc/strategy/swine/index.html?tag=result;title;0]Review[/url]




GTA
(Top Down Action)
0,3 GB
User Score: 7.7
[url=http://www.rockstargames.com/]Download Site[/url]
[url=http://www.gamespot.com/pc/adventure/grandtheftauto/index.html?tag=result;title;2]Review[/url]



GTA2
(Top Down Action)
0,3 GB
User Score: 7.7
[url=http://www.rockstargames.com/]Download Site[/url]
[url=http://www.gamespot.com/pc/adventure/grandtheftauto2/index.html?tag=result;title;3]Review[/url]




Savage: The Battle for Newerth
(FPS/RTS Mix)
0,4 GB
User Score: 8.1
[url=http://www.gamershell.com/download_15298.shtml]Download Site[/url]
[url=http://www.gamespot.com/pc/action/savage/index.html?tag=result;title;0]Review[/url]

Ubisoft has a few free ad-supported games.

Far Cry 1

Prince of Persia: Sands of Time

Rayman: Raving Rabids

You can pick these up with a free account at www.fileplanet.com

[/QUOTE]

I think that promotion ended a long time ago. They don't work anymore

[/QUOTE]

for what i have heard and read is that they no longer function, means that you may be able to download them somewhere (for example on fileplanet from the link cherub_rock has posted...but you cannot activate them anymore to play...furthermore the fileplanet link is no longer featured on their "free games" site.

scroll down here in this wiki article.

[url=http://en.wikipedia.org/wiki/List_of_commercial_games_released_as_freeware]Wiki Entry (Games no longer distributed)[/url]