When a user reports slow performance, a changed home page, and pop-up ads, these are classic signs of malware infection. The first step should be:
Update the antivirus program and run a full system scan: This helps identify and remove any malware present on the system, addressing the root cause of the issues.
Uninstall the suspicious search engine and reset the home page: This addresses the symptom but not the underlying cause, which is likely malware.
Install the latest updates for the operating system: Important for security but secondary to removing malware.
Block the pop-up ads using the web browser settings: Again, addresses the symptom but not the root cause.
Reference:
CompTIA A+ 220-1102 Exam Objectives, Section 3.3: Given a scenario use best practice procedures for malware removal.
Malware identification and removal documentation.