When a windows based DVR System is built, Usually the operating system is contained as it normally would be; on the hard Drive. The hard drive may or may not be the same drive upon wich recorded digital video resides, however the failure of hard drives are well documented, and reloading an operating system and reconfiguring a PC Based DVR can be time consuming. Non PC based, or Standalone DVR systems have an operating system on a chip which loads more quickly, and can be considered far more stable.
Futhermore, Hard drives were never intended to be used in intensive write and rewrite modes as they are with DVRs, and failure happens more often when used in digital video applications.
