Note that many websites have their own advertising, unrelated to adware.
An IE browser helper object that detects visits to known sites and redirects them through a third-party server in order to generate affiliate fees.
Before you can delete the bpboh or mbho DLL, you will need to deregister it. For Windows 95/98/Me, enter one of the following commands:
"%WinDir%\SYSTEM\regsvr32.exe" /u "%WinDir%\bpboh.dll"
"%WinDir%\SYSTEM\regsvr32.exe" /u "%WinDir%\SYSTEM\mbho.dll"
Or for Windows NT/2000/XP:
regsvr32 /u "%WinDir%\bpboh.dll"
regsvr32 /u "%WinDir%\System32\mbho.dll"
After closing all Explorer windows (you may also have to restart the computer), you should be able to delete the DLL and also 'rdxrNNNNNN' in the same directory (the extension will be '.dat' for the bpboh variant, or '.de' for the other variants).
If you have the MSCStat variant you should also delete 'MSCStat.exe', 'adNNNNNN.de.xml' and 'mscNNNNNN.de'. There is also an HKEY_LOCAL_MACHINE\Software\rdxr to clean up in the registry if you like.