ComboFix should not have made any changes that would affect your screen resolution. Most likely it's related to the malware infection you are dealing with and why your brother advised you to run it.
Since you already ran ComboFix, its log should be posted for a thoroughly reviewed in order to ascertain what was detected/removed and what malware you're dealing with. A log should have been created and saved to the root directory, usually C:\ComboFix.txt
Please follow the instructions in the Preparation Guide For Requesting Help
starting at Step 6. When you have done that, start a new topic and post the required logs to include ComboFix.txt
in the Virus, Trojan, Spyware, and Malware Removal Logs
forum, NOT here
, for assistance by the Malware Response Team Experts. After doing this, please reply back in this thread with a link to the new topic so we can closed this one.If HelpBot replies to your topic, please follow Step One and CLICK the link so it will report your topic to the team members.