If you install Avast Internet Security, it will disable windows firewall as Avast internet security has its own firewall. Avast is very light weight on resources and very heavy on viruses. Go for it.
My Computer
At a glance
Windows® 8 Pro (64-bit)Intel® Core™ i5 Processor 2467M (1.60GHz, 3MB...6GB DDR3 System Memory at 1,333MHz (on BD 4GB...AMD Radeon™ HD7550M 1GB DDR3 (Ext. Graphic)