Shall start with the symbols problem first. In my experience, it is usually some spywares and malware problems. Read this list of
MUST GET softwares.
Download them and install in the default location. Update those programs, and scan. Remove anything found. Reboot each time you clean the PC.
Post back how your PC is behaving afterwards.
Note: At any one time, install only ONE antivirus and ONE firewall. Do not have more than ONE antivirus and ONE firewall. You can have more than one anti-spyware programs though.