I use mostly Firefox, but also IE11 on occasion. I use Fastmail for my email service. I received an email from a trusted source which includes a ".doc" attachment. Windows won't open it. Can I add .doc as a legitimate extension so that I can open the attachments? If so, how? In 2nd-grade steps, please! 

My Computer
- Computer type
- PC/Desktop
- Computer Manufacturer/Model Number
- Custom
- OS
- Windows 7 Home Premium 64-bit, service pack 1
- CPU
- Intel box core i5 4460
- Motherboard
- Asus B85MECSM 1150
- Memory
- Kingston Hyper X Fury BLK 1866 8GB 4x2
- Monitor(s) Displays
- Samsung 23" wide-screen
- Screen Resolution
- 1920 X 1080
- Hard Drives
- WD Passport, 1 TB
- Case
- Win Z583 Mini Tower w/ USB3.0
- Keyboard
- Microsoft ergo wave
- Mouse
- Logitech wireless
- Antivirus
- Bitdefender; Malwarebytes Pro
- Browser
- IE11
