File transfer across home network ridiculous speed

So I'm often transferring files from my MBPR to my regular (custom built windows 7) PC and I'm just so disappointed about the slow speeds it's using...

Currently I'm moving a file across the network at such a poor speed that it takes me a long time...
I'm moving a 7gb file and it's taking ages...
Can someone tell me where I can see how fast the transfer rate is?
I was looking through Activity Monitor, and I read data sent: 3mb/s... It can't be that poor can it..?

And is there anybody who has an idea on how to speed this up because I used to be able to do this faster though...

I'm literally sitting right at my router and my PC is wired to the router. So can anybody explain to me howcome this is so slow..?
Are there any tips on how to speed this up..? I've been searching around for a week, but couldn't find a solution on how to fasten it...

ps: I'm not planning on buying a thunderbolt to firewire cable just so I can transfer files.

Thanks for your reply so fast!

I'm using a WRT610N (v2.0). I'm planning on upgrading my router somewhere in the future but would like to get the fastest result I can get for now out of this one.
I've got 2 connections; 2.4Ghz and 5Ghz, but I'm pretty much always connected to the 5Ghz with my MBPR.
I didn't know the option + click thing, just did it, here's the result;

Just found out indeed guys.. Thanks a bunch though!