Problem with IE & Explorer, after SP2

1- one of the main problems I come to you guys IS this problem with my Internet Explorer.
A little background:
Don’t know whether it is due to an incomplete or faulty installation of SP2, but eversince this upgrade, I haven’t been able to use the IE ( version 6 ) !
Clicking on its desktop icon got me nowhere … except another “shortcut to IE” icon appearing on the desktop !
Having purchased my Dell from the States, I see no reason why suddenly ( after installation of this SP2 , by CD - I must add ) have problems validating my windows.
Each time I go through the process of validating, it just stops and gets stuck in the 3rd step of validation( where one needs to install or activate AtiveX from the info bar. Simply because I don’t see any info bar on my IE !! )


The only way to open an IE is clicking on the warning icon on my quick launch tray ( telling me I need to validate my windows and may be a victim of software counterfeiting – when I have NOT changed my original XP Home edition at all ) and voila, an IE opens up but with the following error message:

"SERVER ERROR IN '/' APPLICATION
The resource cannot be found.
Description: HTTP 404. The resource you are looking for (or one of its dependencies) could have been removed, had its name changed, or is temporarily unavailable. Please review the following URL and make sure that it is spelled correctly.

Requested URL: /genuine/downloads/nonGenuine.aspx"



I also have tried to troubleshoot my way, using the Dell “Solution Center” program, which gets me nowhere as I presume it runs on the troublesome IE !!
Ironic, isn’t it ?
( or it could be a mistake in IE configuration or … )

================

2- For the past 2 days, everytime I try to shut down, that error message appears:

It says :

“End program – Explorer.exe

This program is not responding

To return to windows …
If you choose to end the ….”

Sometimes, 2-3 times in a row !
And unless I click on “end now”, it just wont stop!


===========

3- I also cannot use the “defrag” program anymore, as the following message appears :
"MMC cannot open the file C:\WINDOWS\SYSTEM32\dfrag.msc.
This may be because the file does not exist, is not an MMC console, or was created by a later version of MMC. This may also be because you do not have sufficient access rights to the file."

I have also tried typing :
%SystemRoot%\System32\dfrg.msc
in start/run.
But the same message appears !!




BTW, I have already gotten rid of a lot of viruses, spyware and malware ( using bitdefender, Norton antivirus, adaware, spybot, counterspy, … ).
So I assume it cant be any nasty thing like these.