I need to update the .NET Framework to run a new program, but I'm afraid something will go wrong and damage the system. Does anyone have experience - what are the reliable ways to update this component? Should I make backups before updating?

I used a cleaning utility to free up space, but now some essential programs won’t start. Even after trying system restore, issues remain unresolved. It feels like critical files or registry entries were removed by mistake. How can I safely clean my PC without risking important data?