What could be causing my PC to slow down?

There are many potential causes for a PC to slow down, such as:

1. Unused software running in the background
2. Not enough memory or system resources
3. Malware or viruses
4. Corrupted or fragmented system files
5. Outdated hardware or software
6. Registry errors
7. Insufficient hard drive space
8. Incompatible drivers
9. Poor power supply
10. Hardware conflicts