Third independent hard drive with an existing raid 1 array

I would suggest—to minimize any chance of issues—that you back up all your data, format the two drives, and start from scratch. Build a new RAID 5 array in other words.

If you're pressed for time. You can simply add the third drive to your array using the utility you originally used to build your current array. I would suggest backing up your data in any case.

I don't want issues that's for sure..I backup my data every night to a power edge server running MSSBS 2005.

I'm trying to avoid a total "A" position re-start, although the thought of a clean speedy machine has its tempting lures....With your info in mind (thank you)I am still at a loss on how to configure the third drive with the raid bios/boot tool? I can see the drive there and have formatted it there. i just don't see any choose of making it a stand alone drive. I'm feeling pretty dumb at this stage.....you know the guy with the propeller on his hat.......

well obviously you should not add a 300GB drive to an existing 38GB RAID 1(E) array, nor should you wipe it all and start over to create a mismatched raid 5....just silly....A backup would be a good idea anyhow, 38GB is not that much to burn to DVD's....
edit: Oops...you back up you data nightly...missed that part....

Your original idea of a secondary non RAID HDD for the 300GB is really the only option. Is the 300GB connected to the on-board SATA, or the adaptec card ? I'm not real up to speed on adaptecs, but I know some LSI's I have force you to create a 1 drive RAID 0 before it's usable....Dosen't make much sense I know, but it works. After you create the 1 drive RAID 0, the normal INIT procedure can then run, making it presentable to the OS. It would probablly be easier to connect it to the on-board SATA ( if you have it ) and chage the BIOS settings to non-raid. Watch your boot order too, as the on-board will usually have 1st preference by default before add-in cards.

I know the 15K's are fast....I have 28 of them on SCSI U320, but I've retired most of them now....I still use a couple for OS drives though....not much other use for them now-a-days...6U of rack space for 500GB of lightning fast RAID 10 is nice until you get the power bill....LOL

How do you know that it is formatted if you cannot see it in windows? Have you checked it in the Storage manager or are you going by windows explorer? It may be offline there. This is in the control panel under administrative tools-> computer management, then storage. Just right click and set online. Format if necessary. Is that drive just connected to an integrated SATA connector? IS the driver installed to the controller that this hard drive is connected to?