The first thing you should check is that these registry values are correct:
Code:

Windows Registry Editor Version 5.00[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\AboutURLs]"NavigationFailure"="res://shdoclc.dll/navcancl.htm""DesktopItemNavigationFailure"="res://shdoclc.dll/navcancl.htm""NavigationCanceled"="res://shdoclc.dll/navcancl.htm""OfflineInformation"="res://shdoclc.dll/offcancl.htm""Home"=dword:0000010e"blank"="res://mshtml.dll/blank.htm""PostNotCached"="res://mshtml.dll/repost.htm""mozilla"="res://mshtml.dll/about.moz"

If you want, you could just save the above as a .reg file and merge it.  
If you get redirected when typing bogus domain names like www.dfhsaklfddsa.com, rather than just general failures, then this will not fix it. I could not figure out any easy way to change the DNS error page, but it is located in the shdocld.dll file. If you use Resource Hacker to open this file, check the contents of 23\DNSERROR.HTM. Make sure that it does not mention lop.com at all.

It sounds like you got some scumware on your system. Try downloading the latest version of Ad Aware and get the latest reflist file. Run a scan for spyware/scumware and see what it comes up with.

Those are some great ideas, I'll try them out and post up my progress.

Okay you were both right. CUViper, some of those registry entrie were different and had lop.com mentioned in them.
 
PsychoSword, I download AdAware and it came up with lots of references to lop.com and the term "lop" as spyware. It was around 13 references, I am cleaning it up as I type this.

Lop.com, just did a google on it and it appears to be a site which you very well would suspect to be linked to scumware.
 
It could also very well be that some java / active X / whathaveyou deliberately has written in this in your system files. If you found out what did it, please post.
 
I didn't go to the site (I don't wanna have it modiying my settings) but I would expect a ton of popups, collecting cash for the owner.
 
Hammer time, anyone ?
 
H.

Success, I have managed to clean it out nicely and no more problems with it. The problem was also linked to an IE plugin that Adaware removed, a DLL file, and also and a lopsearch.exe file in the Application Data folder. I have my younger siblings also using this PC and its possible they may have unwillingly clicked something or said "yes" to one of those ominious prompts to install something. I decided to post part of the log file of my ad aware cleaning job here.
 
 
Removing selected components:
==============================
Deleting:Doubleclick,3,file,2,,D:\Documents and Settings\Administrator\Cookies\administrator@doubleclick[1].txt,
Deleting:Other,3,file,2,,D:\Documents and Settings\Administrator\Cookies\administrator@valueclick[1].txt,
Deleting:Lop,3,file,2,,D:\Documents and Settings\Administrator\Application Data\lopsearch.exe,203
Deleting:Lop,3,file,2,,D:\Documents and Settings\Administrator\Application Data\plg_ie0.dll,203
Deleting:Doubleclick,3,file,2,,D:\Documents and Settings\Vanisha\Cookies\vanisha@doubleclick[1].txt,
Deleting:Other,3,file,2,,D:\Documents and Settings\Vanisha\Cookies\vanisha@valueclick[1].txt,
Deleting:Doubleclick,3,file,2,,D:\Documents and Settings\Dharmesh\Cookies\dharmesh@doubleclick[1].txt,
Deleting:Other,3,file,2,,D:\Documents and Settings\Dharmesh\Cookies\dharmesh@valueclick[1].txt,
Deleting:Lop,1,HKEY_CLASSES_ROOT,2,clsid\{9b35a850-66ab-4c6d-8a66-136ecadcd904},,
Deleting:Lop,1,HKEY_CLASSES_ROOT,2,clsid\{d44b5436-b3e4-4595-b0e9-106690e70a58},,
Deleting:Alexa,1,HKEY_LOCAL_MACHINE,2,software\microsoft\internet explorer\extensions\{c95fe080-8f5d-11d2-a20b-00aa003c157a},,
Deleting:Lop,1,HKEY_CURRENT_USER,2,software\microsoft\windows\currentversion\backup,,
Deleting:Lop,1,HKEY_LOCAL_MACHINE,2,software\microsoft\windows\currentversion\explorer\browser helper objects\{d44b5436-b3e4-4595-b0e9-106690e70a58},,
Deleting:Lop,1,HKEY_CURRENT_USER,2,software\trinityayb,,
Deleting:Lop,1,HKEY_CLASSES_ROOT,2,swish.browserhelper,,
Deleting:Lop,1,HKEY_CLASSES_ROOT,2,swish.browserhelper.1,,
Deleting:Lop,1,HKEY_CLASSES_ROOT,2,swish.toolband,,
Deleting:Lop,1,HKEY_CLASSES_ROOT,2,swish.toolband.1,,
Initializing:Lop,2,HKEY_LOCAL_MACHINE,2,software\microsoft\internet explorer\toolbar,{9b35a850-66ab-4c6d-8a66-136ecadcd904},
 
Task completed on9:35:02 AM
Done.