To clean up a PC effectively, start by updating your antivirus or anti-malware software and running a full scan to eliminate any threats. After ensuring your system is clean, use the Windows Registry Editor (regedit) to identify any suspicious entries. If unwanted entries remain, consider using a registry cleaner like CCleaner, but only run the registry cleaning feature to avoid damaging installed applications. Windows 7 is generally more resilient to registry issues compared to older versions like Vista or XP. If the PC is slow or websites fail to load, browser helper objects (BHOs) might be the cause, which are often overlooked by standard anti-malware tools. For advanced users, tools like HijackThis can help identify and remove problematic entries, but caution is advised as misuse can lead to system instability. For those seeking to learn more about managing the Windows registry, seeking educational resources or books is recommended, as understanding the registry often involves trial and error.