I bought a Samsung SDE 4001 a few years back which proved to be the worst purchase for a beginner.  I have had to send it back two times and now the DVR has gone again.   
My question: 
The cameras that I still have up ( are connected by cat 5 to the DVR.  Can I replace the DVR with another brand and connect those cameras?  If so, any suggestions, because I have had trouble finding a DVR that has cat 5 such as the Samsung.   
I know this is basic I just don't want to buy a whole new system if I do not have to and I do not have the experience to get detailed.  Thanks!