I now have exact figures for the computer, thanks to a watt meter.
It costs 160 a year to run my pentium 4 computer 24x7, not including monitor, of course without going into sleep mode.
A DVR costs 60 a year to run. I save 100 a year by using a DVR.
If I need to upgrade in 5 years, let say, the DVR, it would seem the better deal. Especially when you consider the additional costs of upgrading computer when things wear out faster. less flexibility with the DVR, the only downside that I can see.