You have tried most of the things we could recommend.
You could do a Restore to the oldest saved date.
Start a "DOS" box and run (as Administrator) sfc /scannow.
Do F8 (or F12, don't remember which for Vista) at the Boot, and do a repair install. Be sure to save all your data on an external hard drive or on DVDs.
Do a complete OS recovery to the "as received" OS.
Because by-passing the router also did not help (is it wireless?), you may have either a busted OS or some faulty hardware, ethernet /wireless cards. Did you try a complete system diagnostic (F12)? Have you tried a new ethernet cable?
Hey all,
This problem is driving me absolutely crazy and I am really hoping SOMEONE can help me! The problem is my broadband internet connection has gone from being really fast for the last year to excruciatingly slow all of a sudden last week, and it has stayed that way. This happened once previously a couple of months back and getting rid of an old expired copy of Norton antivirus fixed it up straight away. But this time I've tried what seems like every single thing i've read in every web forum that has solved the problem for other people, but with no success.
Things I have tried;
Cleared browser caches
Tried in both IE and Firefox
Disabled phishing
Confirmed that my ISP has nothing to do with the slow speed
Tried plugging directly into my modem, ie. bypassing router
System restore to before the problem started
Switched off IPV6
global autotuninglevel=disabled and ipconfig /flushdns
Uninstalling all the windows updates from around the time the problem started
Changed my power setting to maximum performance
Have tried starting in safe mode and it's still the same
And what seems like a million other things that I can't even remember now because this thing is driving me so crazy!
Have run spyware and malware scans and they came up with nothing
Virus scan (I use Avast) also came up clean
Another computer in the house running XP is still fast
I've heard some people mention rolling back driver network cards...but I can't do this as the option is not available as it has never updated
OS: Vista Home Premium
6.0.6001 Service Pack 1 Build 6001
Hewlett-Packard G6000 Notebook PC
I think I would literally be the happiest person in the world if one of you can help me solve this..
I'm not really all that knowledgeable when it comes to computers so if any of what i've typed above doesn't make sense or is silly or if this is in the wrong section I apologise, and also if there is any other info I need to provide just let me know
Thanks in advance! 
Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic