Netgear A6200 wireless adapter is disconnecting from the internet.?

[Alli]

I have recently received a hand built computer from a friend. In other words, this is a brand new computer that has only been used once before. I use to have a WNA1100 that I used for my last dell computer. That did not work for this computer, so I went ahead and bought a new one (The A6200 adapter) to try to get it to work for my new desktop. The problem I'm having is that I can connect to the internet for a short while, then after 15-20 mins, the wifi disconnects and in order to restore it I have to disconnect the adapter and plug it back in. I have the drivers for Windows 8 which is my operating system. I called netgear tech support several times, each time they tell me to re-install, but after re installing it over ten times, I don't think that is the problem. Troubleshoot is telling me multiple things. The most reoccurring is "default gateway not available" (something like that) To fix that I unchecked the box in the device manager that lets my computer shut off the adapter to save power.
I'm looking for any other possible solutions, If you require any other information, please let me know, and I will be more then happy to supply the information.
Thanks!
I thought that might be a problem so I actually bought a new router. As for the "Immune" statement. I wasn't implying that it doesn't have it's own problems, I was informing people of my desktops current condition.

[Nisia]

"I have recently received a hand built computer from a friend. In other words, this is a brand new computer that has only been used once before."

Just that because it's new it does not mean that it's immune from having defective parts.

You may have too many wireless devices connected and your router dies.

[Boss]

It might be faulty.