Can I install 800mhz ram in a first generation machine?

[Crugga]

Sorry its probably been posted loads but I cant find the exact question.
Ive been offered 4gb-2x2 of crucial ram for £30, its 2008 spec 800mhz.
I just wondered would it work ok in my first generation MP?, and if so would it be ok mixed with the original 667mhz ram?
Ive read conflicting views where some say its compatible but will only run at 667 which is fine but then ive also read that it has to be 100% correct.

Thanks.

 

[gullySn0wCat]

It will work at 667mhz. Done!

 

[DanielCoffey]

It is still a good price - you could try it and resell if it gives any issues.

 

[Crugga]

Thanks.
Going to grab it off him later in the week.
As you you say its a bargain so it'll easilly shift