Every PC needs an anti-virus program, but Windows 8 (and Windows 8.1) users don’t need to buy one.
Windows 8 has a built-in product called “Windows Defender” which provides basic anti-virus protection.
You’ll probably be urged to buy McAfee or Norton if you buy your Windows 8 PC from PC World, but it’s not necessary.
If you install Norton or McAfee (or most other anti-virus programs), they will just disable Windows Defender.
If you then uninstall Norton of McAfee, make sure they (or you) have re-enabled Windows Defender. Go to Control PanelSystem and SecurityAction Center
You can run MalwareBytes alongside Windows Defender. The paid-for version is an excellent way to suppement the capabilities of Windows Defender (and does a much better job, in my experience, than Norton or McAfee).