Raid 1=Format?

Ok I wish to add hard drive for raid 1 do I have to reformat my first hard drive,the one with all my data.Would like to keep the data!.I have windows xp pro

No, RAID 1 means mirroring the entire drive contents, however there's always that chance that you'll lose data.
What hard drive do you have now, and is it IDE or SATA. You motherboard supports both SATA and IDE RAID.

You should have the option when you setup the array to copy the 1st drive onto the 2nd (empty) drive. Make sure select the correct drive as the master, or all your data will be gone.

Also, make sure you install the RAID driver in windows before setting up the array, if you don't windows will not boot.

Make sure you backup any important data before doing anything.