Is that the reason that you replaced your hard drive?
Were you having internet problems BEFORE you replaced the hard drive - or has that happened only now, after you replaced the HD?
Do you still get poor internet, if you plug your MBPro directly into your router with an ethernet cable (or is wireless your only possible choice?)
Finally, what exactly do you mean by "internet speed is awful"? What are you using to test that?
will give a decent test, which can give you some actual numbers. Run it a second time, after restarting your wireless router (just unplug, then reconnect the power cord on the router itself). Also, restart your MBPro. Don't run ANY other software, other than your browser, and try that speed test again.
That will give you three different sets of operating conditions, so you can compare the numbers, all after running the same test site.
You could also try the test running Safari, rather than Chrome - you may find that can make a big difference, too.