Slow internet only on one computer of network

I have: 2 desktops, 2 laptops, 2 Samsung Tablets, 1 Kindle Tablet, 4.3" Proscan Tablet, an Android Phone and an iPhone 5s...all on my home network.

All computers, tablets, phones...are updated but only on the one laptop the internet seems almost like it's cutting in and out or very very slow. I updated my network driver to see if that would help and it didn't. Ran all kinds of diagnostics with no conclusions. Called the internet people who ran a test on my line with no problems detected. I don't know what else to do. They did send me a new modem which imo made the problems worse but I did have the problems before the new modem as well. I completely did a system recovery back to out of box state because I hadn't done it in awhile and thought maybe a fresh os will help but nope still having problems here and there. It doesn't matter what time of the day either. And no one else on the network is having problems.
If someone could please help I'd be greatly appreciated. Just let me know what other information you need.

Basic information windows 7 64 bit HP laptop fully updated via windows update and hp support assistant.

Did you do a virus check? and, did you try it in safe mode with networking support?

I ran free AVG with nothing found and malewarebytes with nothing found. Also like I said I restored the computer to out of box state still no viruses or anything and still same problem.

Did you check for the router settings? did you try a router reset?

Maybe there's something set in the router concerning the MAC address of that specific PC? or the assigned IP, do you use DHCP, or static IPs? that's why I would recommend a "restore factory settings".

I did a reset on the modem and I rebooted the modem still same problem. I don't know if it's DHCP or Static IPs. How do I check? I know DHCP is enabled. Security is set to WPA2-Personal Encryption: AES

The router and modem are an all in one deal.

Any other information you need?

Not just a reboot, a total reset

Yes I did both. I hit the little reset button on the back of the model for so many seconds.