IE7 doesn't work

Hii everybody,
My computer runs on Vista.
my IE7 shows: cannot display this web page always though am connected to internet..but the craziest thing is that Firefox works fine.
once I try to load an anti-virus program it downloads fine but once I install it tells me it cannot find a secure internet connection.i tried resetting IE7.but it ened up with shoddy result and now i vehemently noticed that IE7 once it starts up, shows: DNS-error.
have you any of you guys experienced the same situation like wht im currentlyi goyng through????

1. Clear your browser cookies.
2. Open your CMD (Start > Run > "CMD")
3. Run the following 3 commands:
* ipconfig /flushdns
* ipconfig /release
* ipconfig /renew
4. Type "exit" or just close the CMD.

*get a new version of explorer
*uninstall the one you currently have on your pc

if you are unable to see IE7 in Add or Remove Programs follow these steps:
* Click Start
* Click Run
* Type or copy and paste, into the text box:

%windir%\ie7\spuninst\spuninst.exe

* Then Press Enter
* Restart your computer.
* Install the fresh version of Internet Explorer.

try this steps during installation.

1. The first thing to do is READ THE RELEASE NOTES. There are known issues and you may save yourself hours of grief if you make sure you are informed before you install IE7.
2.
Set a restore point (just in case).
3.
Turn off Automatic Updates (believe me, you'll thank me later if you've already installed an IE7 beta or RC build).
4.
Disable protective software such as antivirus, antispyware and crash guards.
5.
DO NOT TURN OFF YOUR FIREWALL!!!
6.
Stay connected to the internet.
7.
Shut down all running programmes - that includes Messenger, Windows Defender, and OneCare - don't forget to check the systray icons as well.
8.
If you are running ZoneAlarm 6.5, disconnect from the internet, uninstall ZoneAlarm, make sure Windows Firewall is enabled, reconnect to the internet then install IE7. This is because ZoneAlarm was blocking access to the Windows Registry. Yes, you have to uninstall ZoneAlarm.

IE7 Gold's installer runs various registry permission checks before installation starts to minimise the risk of aborted/damaged installs, but there is no guarantee that the installer will pick up everything. It is best to ensure that problematic software that may block access to the registry be disabled.

If you still see registry permission problems, please check out the advice here:
http://blogs.msdn.com/astebner/archi...04/739820.aspx
9.
HKEY_Current_User\Software\Microsoft\InternetExplorer\InstalledByUser

IE7RC1 installations failed if the DWORD was not there, but the installer also deletes the DWORD after installation of RC1 is successfully completed. You won't find it on a standard RC1 installation, but at the same time, the existence of the key is not known to cause a problem. When the missing DWORD caused an installation failure with RC1, all that happened was the install rolled back, you saw the failure window, and a shortcut was dumped on your desktop. So, if you wish, you can try adding the DWORD if you have a mysterious installation failure that you have trouble finding a cause for, but I doubt it will make any difference - it certainly hasn't made a difference on any of the dozens of systems I have worked with.
10.
Install Internet Explorer 7. Reboot *twice* before running your new Web browser for the first time.
11.
Don't forget to re-enable your antivirus, third party firewall and other protective software now that you're finished.
12.
Do not reinstall any version of Microsoft Windows in any way after you install Internet Explorer 7. Do not upgrade Windows in place or upgrade to a new edition. You must uninstall IE7 and reboot twice before attempting to repair, reinstall or upgrade Windows: