Hi,
Resetting the router means to set the router back to its factory settings, there is a reset button at the rear of the router. Do not try it yourlself. Call the router company and ask them to walk you through the process. Also tell them that you need to update the firmware of the router. Updating the firmware improves the performance of the device. Do mention that you need to enable the security on the router. Once the security is enabled then you can be sure that no one else is using your wireless network.
This should make a lot of difference if the problem lies with the networking part, I mean the router and the security etc.
If still the problem persists then we need to check all the system's for any virus or spyware infection and probably would need to do a clean up job and adjust some settings to improve the performance of the system's. I will tell you how to do that in the next post.
I am a former Dell technicall support specialist and all I want to say that this is a very common issue and very easy to fix. We just to follow a systematic approach to isolate the root cause.
Good Luck!!