i got 2 500GB harddrives and would like to set up a raid to avoid data loss. both are from the same vendor but they are not the same model. can i set up a raid or do i need some special hardware for this?
You can set up what is known as software raid through Windows. Read more here: http://www.howtogeek.com/howto/36504/how-to-create-a-software-raid-array-in-windows-7/
According to this, you can, but be advised that you will have only 500GB available according to this source. http://www.pcworld.com/article/132877/RAID.html
There are several RAID levels but with only two disks, you are somewhat limited to RAID 0 and RAID 1. As you are looking for redundancy, RAID 0 (striping) is excluded so RAID 1 (mirroring) is left.
Both of your disks have the same size and this is optimal with mirroring (otherwise, the extra size of the larger disk will be wasted).
Finally, you do not seem to have specific hardware to handle the RAID setup. This is fine too. Software RAID has actually several advantages compared to hardware RAID.
You do not tell what OS you are running but if you are lucky enough to run an OS that support ZFS, that would be the safest solution for your data and the simplest one to configure. Moreover, you could also leverage the built-in compression to increase both of the capacity of your volume and its overall performance.