RAID 1 means you have essentially two separate drives with identical information. So breaking the RAID is simple. Boot to the Intel RAID Option Rom Utility (ctrl + I ), change both drives to NON-Member disks then reboot. The 2nd drive will be assigned new drive letter, and you can reformat it using disk management, and have additional space.
Well, there is no 100% foolproof method of breaking your Raid pairing and not losing data. The only way to ensure you don't lose anything is to practice the "Grandfather Principle" of Data Processing. That is, you need to make an external backup of your existing critical data onto an external device such as an external hard drive, flash drive, cd/dvd disc(s), or Cloud backup such as CloudDrive or GoogleDrive. Once you make that back--say onto a flash drive, you then need to make a SECOND backup onto a different external media type; choose one of the others from the above list (external hdd, cd/dvd disc(s), or Cloud Backup).
This will be the best protection you can get approaching 100%. If you really want to do it right, store the SECOND backup offsite at a close friend's or relatives home in case you home gets hit by a natural disaster (flood-fire-earthquake) or loss of your computer via theft.
If you do all of this, and your "Raid-Breaking" bad (couldn't resist the pun there) fails, you have 2 chances to get your data back onto the boot drive. Of course the methods that bassfisher and I suggested to you says you can break the Raid pairing and reformat the 2nd drive in your Raid config and use that for one of your 3 backups! Of course, that may or may not work. As I worked for multiple companies that produced RAID drive systems I can tell you automatic backup upon RAID unpairing doesn't always work as there are a large number of variables that can cause you difficulties, not excluding Human Error.
You still won't be at 100%, but you'll be awfully darn close!
Good luck and please make sure to let us know your result. Your Post could help someone else attempting to do this.
How I Migrated an OS RAID1 Array Over To another Single Disc Drive With No Data Loss .
The above is for poor souls like me doing a search.
Windows Seven Pro
Motherboard - Gigabyte GA-EP45-UD3P
HDD's - 2 Western Digital 750GB RE3
The on board Intel Raid.
The destination drive, a Western Digital 750GB Caviar Green AACS-00ZJB I had laying about.
The Ware: Acronis True Image Western Digital Edition from their downloads site.
Acquire The Acronis Ware.
Acquire a Hard Drive suitable for the job.
Shut the system down.
For the sake of having a backup - Disconnect one of the RAID 1 drives. (I pulled the 2nd in the list of the two. Not sure if it matters)
Install and connect the Hard Drive you want to become the single OS system disc. (No need to have it formatted Acronis will do this)
Boot up. If you have the boot screen showing during boot you see the "degraded" message in the RAID status.
Start up Acronis to the cloning section and I chose the auto or express recommend method over the advanced.
It will ask you to select the Source and the Destination from the list of what it sees, and for confirmations. Let her rip!
It will ask you if you want to shut down when complete or something else, I forget but I chose the default choice to shut down.
When complete (I returned after mowing the yard an hour later and it was shut down) removed the remaining RAID 1 drive. (I did some rearranging of the drive location in the bay and cable routing and moved the SATA cable to a port on the motherboard of my choice)
Boot up. Done!
In my case it was like nothing happened. Everything was in place. I also still have my original Raid array intact. But I am doing this to get my hands on the two drives for other purposes.
You may be able to use one of the Arrays drives by discounting it, then connecting it to another port, booting to see if the array is degraded, letting Acronis do its thing, disconnecting the remaining array drive and booting. But this is for the brave of heart. And I'm not sure it will work. You may need to format the drive some how 1st.
Of course the methods that bassfisher and I suggested to you says you can break the Raid pairing and reformat the 2nd drive in your Raid config and use that for one of your 3 backups! Of course, that may or may not work.