Troubleshooting Internet Explorer on Vista Locking Up or Running Slowly

If you are having issues with Internet Explorer running extremely slow, crashing, locking up, or just generally behaving badly, there are a couple of troubleshooting steps that you can follow to likely fix the problem. And no, I’m not going to just tell you to install Firefox.
Of course I’ll suggest it, since Firefox is an excellent browser… But for most people, Internet Explorer works just fine and does everything you need. So let’s get that browser working properly again!
Test Using Internet Explorer’s "Safe Mode"
The first thing you can do is run Internet Explorer with all the add-ons (or plugins) disabled, which will help us determine if the problem is caused by an add-on or somewhere else in the system.
You can find the "Internet Explorer (No Add-ons)" menu item under Accessories \ System Tools in the start menu, or you can launch IE from the command line with the -extoff switch like this: iexplore.exe -extoff

If the performance / locking up problems are gone, then you know you are dealing with a problem add-on, most likely one of those toolbars that seem to be attached to every shareware application.
Disable Internet Explorer Add-Ons
Close the "safe mode" IE window, and then open Internet Explorer normally. Click on the Tools menu, then Manage Add-ons, and then Enable or Disable Add-ons:

 In this screen, you can select Add-ons and then choose to Disable them one by one using the radio button at the bottom.

 The default list shows only the add-ons that are currently loaded, so you should also check out the other selections, because the problem add-on might not be set to load on startup.

In order to properly troubleshoot, it would be easiest to disable all of them, and then re-enable one by one until you find the problem add-on (which you should uninstall if possible)
Reset All Internet Explorer Settings to Default
If you are having too many issues, you can always just completely wipe the slate clean and start over with a fresh Internet Explorer configuration, which should fix the vast majority of issues.
Open the Internet Properties dialog by finding the Internet Options section in Control Panel (just type internet into the search box)

 (Note that you can also right-click on the Internet Explorer icon on the desktop and choose Properties, or just use Tools \ Options if you are able to open Internet Explorer)

Once there, choose the Advanced tab, and then click on that Reset button. Everything will be completely wiped clean, but it’s likely you’ll have better luck browsing from then on.
Scan Your Computer for Viruses/Spyware
This should be a given… anytime your computer is running extremely slow you should scan for viruses and spyware.
Disable Receive Window Auto-Tuning
If none of those fixes the problem, and you are just having a really slow browsing experience only on your Vista computer, the problem could very well be due to the network auto-tuning feature in Windows Vista which is incompatible with some routers.
Open up an administrator mode command prompt (right click on command prompt and choose Run as Administrator), and then type in the following command.

netsh int tcp set global autotuninglevel=disabled

You’ll have to reboot the computer after making this change. Note that the same change also can help fix problems with copying large files.
Re-register actxprxy.dll
According to Windows expert Ed Bott, if you are having issues with Internet Explorer running really slowly, you can re-register the ActiveX Marshaling Library (which is also buried in a Microsoft article).
Open up an administrator mode command prompt (right click on command prompt and choose Run as Administrator), and then type in the following command.

regsvr32 actxprxy.dll

You’ll have to reboot the computer after making this change.
Reboot Your Router!
I can’t tell you the number of times that my browsing experience slowed down to a crawl because my Linksys router needed a reboot. This seems to happen a lot more if you are downloading torrents as well.