Internet suddenly slow on one computer.

Hi,

I'm new on these forums, and it seems like the place that can solve the problem that's been affecting me for the last few days.
As of recently, the internet on my computer has been been relatively slow for the majority of times.
My internet is prone to being slow when everyone in the family is using it, however, as of recently, it's been EXTREMELY slow and laggy when I play games and browse, and I have no idea why.

I tried system restore, reinstalling/uninstalling my network card drivers.
I use a TP-Link W951N V1 network card on my desktop computer.
Other things, I use a 2wire 2701 HGV-W router. (relatively old, yes. Yet, still works efficiently.)

I know I'll need to provide more info, so I'll update as questions are asked.

Thank you!