Trouble with old DVR and new PC: Can control DVR with Video Server S, but no video

[Frank H]

Hi,
I've got an old (maybe seven or more years) 4CH DVR (unbranded model 771-A) and an equally aged Video Web Server (unbranded 732S). They've been in storage for the last four years but I dusted them down and everything seems to work OK. I can see the DVR direct on the TV monitor. When I installed Video Server S on my Win7 IE8 PC it installed fine and runs and I can control the menu and the cameras through the Video Server S software BUT I can't see any video at all. Same thing if I run the browser based DVR controller, the buttons all work and 'push' the buttons on the DVR but there is no video.
What have I missed out with my setup?
Thanks