The dial up window keeps appearing without prompting
Go to IE tools/internet options/advanced and make sure the option to automatically check for IE updates is turned off. Otherwise, there is something trying to access the internet. Do an inventory of your programmes to check for any likely culprits.
Go to start/run and type MSCONFIG. Check the start up tab for any possible culprits.
It is essential to check for spyware/hijackware/foistware.
Go to IE tools, internet options, general tab. Click on the cache settings button and then 'view objects'. Delete anything you don't recognise. If you are unsure, or no objects appear, for diagnosis purposes I REALLY like BHODemon, available at click here. It does not need installing - simply unzip and run the EXE programme. It is very easy to use.
I find this programme is a better option than IE6's ability to turn off "Enable third-party browser extensions (requires restart)". This disables *all* plug-ins and makes troubleshooting very difficult.
Many people like AdAware, available at click here . Make sure you keep the signature files up to date and remember, AdAware may only remove the current installation of spyware; it may not do anything about software that reinstalls itself, so unless you want to get stuck in an endless loop of hijack/cleanout/hijack/cleanout make sure you get rid of whatever is installing the junk. See my Troubleshooting advice for information about how to track down and get rid of spyware completely.
An excellent replacement for AdAware is Spybot. Again, it is a free programme which can be downloaded from: