Adding it as a non-steam game won't let you re-validate the game files.

Make sure you have this installed as well.

fixed it but i can play for a little bit but then it crashes and i get a unrecoverable fault error....

Do you have any modded vehicles?

yes two just two and they are both els enabled....

That could be the problem. Is it an SMPA60 error?

If so, remove your car mods.

no but its only when i use on of the cars i can give you the name of it.

What do you mean on of the cars?

To many downloads can cause this problem, to many mods download that is, it might doesn't lag the game, but it affects CPU Measures and makes the game have to stop running and crash it. I don't know about this problem, that might be the problem but I'm not sure. Just keep following Iconography for help.

no like when i use the FresnoPoliceCrownVictoria i can play all day thats why it takes so long to reply but when i use the GTA4 Unmarked FCVs Pack it crashes the game when i select it to use or get in it when it spawns randomly around the map it crashes then game other mod car doesnt crash it.

Using multiple car mods can crash the game. I have used the Unmarked FCV pack and it did not crash for me but I have a powerful system.

Not every mod will work on every computer. If the Unmarked FCV pack doesn't work, do not use it.

it works but when i use it it crashes the game.

No you can't. You have to re-install.