I've got an old netgear dg834g router and I want to set it up so that it connects wirelessly to the main router in the house (netgear dgn3300) in order to have wired connections from the old router to my pc and xbox 360 upstairs.
I think I need to change the setting on the old router so that it acts as a 'repeater with wireless client association' but on the most recent firmware this doesn't seem to be an option.
While it might be a simple misconfiguration on your part, it's also very possible it’s a WDS compatibility problem.
WDS is NOT a wifi-certified protocol, so implementations vary, making WDS incompatibility all too common. You're most likely going to have success when the devices are all from the same manufacturer (which is the case here). But even then, manufacturers are known to change it across product lines too! It's not at all unusual to find out ALL the devices must use the same make, model, and hardware version for WDS to work either at all, or reliably.
That's why WDS has long since been replaced w/ universal bridging, which is based on the standard B/G/N protocols.
Fortunately, WDS is not a particularly complex setup. You enable it and specify the MAC address of each device to the other. If you’ve triple checked your MAC addresses, and have encryption OFF, and it still doesn’t work after a hour or two of trying, it’s probably just incompatible. So don’t drive yourself crazy over it.