TheOneOverTHere :
so if i have a one hdd nearly full so does raid just work ? Or do i lost all of my data ? like 500gb of games and 300 gb of programs and i need to download them from net and i dont have time or enought fast connection to download them
Then you wont be running raid.
With only two drives your options are raid 0 or raid 1.
For raid 0 you will lose all data on the drives when you create the raid array.
For raid1, some raid controllers are able to mirror the existing drive to the second drive while other controllers force you to create a raid pair thus losing all you data. You do not gain any space with raid1 so it doesnt help you.
Since you still have 200gb of space left, I suggest you use this drive to create a backup for when your main drive dies. It does not sound like you have one. Then you can work on saving up for a 2TB drive. When you get it you can then backup the 1TB drive to it and then put the backup 1TB into the pc to use as more storage space.