Hi i am building a new comp for the first time I want fast access to the drive but used to use 2 drives previous, one with the operating system and one for storage,just incase of fatal crash.
I have heard about RAID 1 but worry like my previous setup it will run slower than a single 500 drive
Help....???

Sure, it will likely be a bit slower, but if a drive fails, you won't have lost your data as in your previous system.

raid 1 will be faster, but more likely of loss. If you don't load extremely large files over and over (the os doesn't count), you don't really need raid. I use raid 1 myself, but also have a 3rd drive just for backup.

I myself have 4 drives, 1 for OS and programs, 1 purely for backup, and two RAID 0 toegther. I also have windows backing everything from the main and RAID drives DAILY just to be sure.
I think the better question is how sensitive and critical is the stuff you're working on? I back-up all the time because of the risk associated with RAID 0. Before I was doing that I only backed up once in awhile because everything was fine and nothing was that critical.

The point is to focus on your needs. If it's not critical to back up constantly, then there is no need to RAID 1 the drives. That will then give you more room to use the computer for other things. Also, when you RAID 1 them it will be the smallest drive size x2 so if going to do that make sure they are at least the same size of drive.

You can also go and do the external HD as well for back-up. They are getting very cheap of late and then backs up outside of the computer.

Lots of choices available.