What is the Maximum Amount of RAM a Windows 7 computer can handle ?

Windows 7 can Handle Maximum 4 GB of RAM (32 Bit processors)
Minimum Amount of RAM is 2GB

How to boot a Windows computer in safe mode?

Safe mode is a troubleshooting option for Windows that starts your computer in a limited state. Only the basic files and drivers necessary to run Windows are started.

To boot a Windows computer in safe mode do following steps
1. Restart your windows computer
2. Press F8 when boot menu appears (If your computer has more than one operating system, use the arrow keys to highlight the operating system you want to start in safe mode, and then press F8.)
3. On the Advanced Boot Options screen, use the arrow keys to highlight the safe mode option you want, and then press Enter.

Minimum requirements to install Windows 7 and Windows XP in a PC

If you want to run Windows 7 following are minimum requirements

•  1 GHZ or faster Processor
• 1 GB RAM (for 32 bit processor), 2 GB RAM (for 64 bit processor)
• 16 GB available hard disk for 32 bit. 20 GB for 64 bit
• DirectX 9 graphic device with WDDM 1.0 or higher driver

If you want to install Windows XP, following are the minimum requirements

•  Pentium 233 MHz processor
• At least 64 MB of RAM
• At least 1.5 GB of availiable space on hard disk 

Where is the Hosts File located ?

In operating system hosts files are used to maps host names to IP address.

It is located in \system32\drivers\etc\hosts