Simple Document Backup

I have been using Memeo Backup for some time, and it seems to do what I would like - it monitors my activity, and when it identifies a new or changed document it copies it to a largs exernal disk that I use for backup. However, it seems to be badly affecting performance and so on (in that the performance difference between running with it on and off is significant). I thus would like to replace it, and i suspect that I need something more passive (that is it backs up my documents at a set time) as the think I like about Memeo (Monitoring changes) is the thing that slows my system down.

Can anyone make any suggestions which system I should use? My requirements are fairly simple:

I would like to be able to define the directories I back up
I would like it only to back up changed or added files (i.e only do a delta backup)
I would like to be able to recover individual files as well as the whole system
I would like to be able to set up when I want it to back up

Would you suggest the inbuild Windows backup system?

I like FileBackupEX, but there are many others.