I have a GA-P35-DS3L board.  No Raid Controler on chip.
Now I want Raid.
My question is a Raid Card a better choice than replacing the MB?
And which Card or MB?

Yes probably a RAID controller will be better.  I do not know of a reputable one to recommend for you but I can offer this... Why RAID?  Unless you plan on running SQL, doing some major file transfers on a regular bases, or running MS Exchange on your computer... there's no point.

If you use a RAID card, you could probably move your array to another PC later.  If you use mobo RAID, you probably won't be able to do that.  I haven't used RAID since SCSI, so I don't have the personal experience to recommend something.

Thanks, I was beginning to think that I was invisable.
Why Raid?  No other reason than I want to.  
Oh, a card would (might) enable moving my array to another PC later.  
I like that.
Anybody have experience with Raid Cards?
 

Most of the Intel onboard Raid controllers (e.g. ICH6R .. ICH9R) are upwardly compatible.  Tom's did an article on that a while back.  You wouldn't be able to swap to a different chipset's RAID controller or a secondary controller, however.
 
What RAID mode are you considering?  RAID 0 isn't RAID at all, and can be done in Windows I think?  RAID 1 doesn't place much add'l load on the system.  But RAID 5 can be a bit slower, especially if you turn off WBC in which case it is a LOT slower with onboard controllers.

RAID 0.  
I dont know about being able to RAID 0 in windows.  You can?
 
I did a google on windows RAID.  Software RAID.  I dont wan't that.  The OS has to be installed before the RAID.  I want the OS in the RAID also.  That way won't enable that.

Some flavors of Windows enable software RAID 0.  Some enable RAID 1.  Some enable RAID 5.  I honestly don't recall which ones disallow RAID 0 or RAID 1, so you may be right that these aren't options in your config.  There is a hack to make even RAID 5 available (you make the O/S think you're running Win 2K3 Server, or something like that), but I wouldn't recommend such a hack given the possibility of future incompatibility.
 
I use RAID 5 and (R)AID 0, each for a specific purpose.  What RAID mode do you want to use, and what do you want to do with it?  Do you want performance?  Availability (uptime)?  Capacity?  What do you do with the system?