Maximum PC

Hi guys. I'm hoping somebody can give me a clear-cut answer on this issue that I've been having, as it is quite literally driving me mental. The story behind it is that roughly two weeks ago, my network speeds dropped off, from around 45mbs to only 2mbs(as tested by speedtest.net). I've tried everything that I can think of to troubleshoot this issue, and it completely dumbfounds me that I can't work it out. A list of the things I've tried includes:
-installed new drivers
-releasing/renewing IP address
-reformatting computer (this has made me very sad, as I am now downloading updates painfully slow)
-restarted computer, modem, router, many times over
-I have plugged directly into the modem, but with the same results (it isn't the router)
-I considered it being hardware, my motherboards nic perhaps, and so I went out and purchased a d-link pci-e network adaptor, only to find the speeds were exactly the same wirelessly
-I have called my ISP numerous times, following their generic, unhelpful, troubleshooting routines
-I cried a little, hoping it would feel sorry for me
-Ran virus and malware scans in safe mode
-Tested download speeds in safe mode, but was still the same
-I have connected my laptop, both wirelessly and wired as well, only to find it unaffected by this annoyance
-I cried some more...
So, please let the helping begin! However, there are a few things that you should know first. 1. Web pages load quickly, just the way they are supposed to, but when trying to watch videos on youtube and such, there's a bunch of skipping, pausing, and all-around slow loading times. 2. Even though speedtest.net and speedtest.shaw.ca both show my slow download speeds, speakeasy.net shows my speeds to be around 25mbs. 3. My upload speed isn't affected (3mbs steady). 4. After restarting the computer and reinitializing the modem, my first speedtest after reconnecting will show speeds up to 40mbs for all of 8seconds, before dropping down and remaining at 2mbs.
I think that's about it. Anyways, thanks for any replies in advance; any and all help is appreciated.

Peace

P6X58d Premium Motherboard Core i7 930 oc'd to 4.1ghz 2 GTX580's in SLI 24Gigs DDR3 1866mhz Windows 7 Home Premium

It seems like you have pretty much ruled out the possibility of a software problem. What I take from your post is, your laptop is unaffected?

How many wireless devices do you have connected to your router (I know you mention the problem persisted with a direct connection to the modem)? Do any of these other devices, besides the laptop, have problems?

What tier are you paying for? I see your ISP offers several different tiers each with a data cap. I am assuming you are using the Broadband 50 package (50 down and 5 up) with a cap of 400GB. How often are you using streaming video/radio/anything that streams?

Also, can you try doing a Ping Test? You might also try something like OpenDNS (I know you mentioned your laptop is fine, but would be an interesting troubleshooting step).

Hi, thanks for the reply. OpenDNS wouldn't be helpful here, as that would only allow webpages to open faster, which I'm having no problem doing. The ping test is something I should've mentioned as well, for I am getting roughly 10-15ms pings, and zero packet loss. The jitter is minimal as well. I have used Bittorent in the past, and I thought maybe somehow my internal IP could be blocked, or limited, and I called my ISP to ask them about it. They said "we can't limit the downloads to an IP of one computer while all the others get full signal. As I've tried it directly connected to the modem and also behind my router's IP, I would have to agree with them. It is really frustrating. The only other thing I can think of trying is to take my computer over to my folks place, and plug into their router and see if i get similar results there. There is no way that my onboard Nic and a brand new Pci-e network adaptor would post the same speeds is there? If it was a hardware issue that is?