Hi Carla, welcome to itsallPC

The first best thing to do would be to run some hardware diagnostics, including a memory diagnostic and Hard Disk Drive surface scan.

For the memory diagnostic, I recommend Memtest86+. You will need a floppy disk (for floppy version - current at date of posting) or blank writable CD (for ISO version - current at date of posting). Allow the diagnostic to complete at least 1 "Pass".

For HDD diagnostic, I will need to suggest a manufacturer specific utility, but I cannot do this since you have not given any details about your system.

Because you are new to itsallPC, I strongly suggest you read this.