Unusual Slow Internet Connection problem w/VPN in Vista Home Prem

[Guest]

I have been using Vista Home Premium on a new HP laptop for almost a week now
and have not had any problems with my internet connection until after I setup
a VPN connection for work.
Since the VPN connection was setup, my internet connection at home goes very
slow on most sites (but not all), until I log onto the VPN.

Once logged onto the VPN connection, I do not have any trouble loading
websites. The internet connection becomes blazing fast, as before.

The browser I use is not affected nor the cause of this, as I have tried
both Firefox and Internet Explorer.

Is there a fix for this?
I have already tried resetting the protocols to not use TSL and to use only
SSL, disabled all add-ons, used "netsh interface tcp set global
autotuninglevel=disabled," even tried running without the Firewall and
Anti-Virus software (Webroot Spy Sweeper).
My network adapters are "Intel PRO/100 VE network connection" and "Intel
PRO/Wireless 3945ABG Network Connection."

 

[Guest]

That fix doesn't address my problem - the VPN speeds up my connection. It
does not slow it down.

Curently, I'm trying turning Windows Defender off and seeing if that's the
problem. I've noticed that the slow down occurs after I've been on the
internet for a while. Restarting my computer after turning off Windows
Defender seemed to fix the problem, but I'm not sure of that yet.