How to block a contact in Gmail?

1. Click Contacts from the left side of Gmail.
2. Select the person you'd like to block.
3. Select Block from "Show in chat list" Box.

To unblock 
Just select Always or Auto from the "Show in chat list" Box.
OR
Type their name in the Search, add, or invite field at the top of your Chat list. Then, in the blue box that appears, hover over your contact's name and select Show in chat list.

How can I disable Autorun?

• Click Start --> Run
• Type GPEDIT.MSC
• Go to Computer Configuration --> Administrative Templates --> System
• Locate the entry for "Turn off Autoplay"
  
• Double click and change it as you want.

Remove Autorun.inf Virus

1. Open command prompt. Go to Windows, then Run, and type "cmd" . Press enter.
2. Type "cd\" and press enter to get to the root directory of c:\ .
3. Type "attrib -h -r -s autorun.inf" and press enter.
4. Type "del autorun.inf" and press enter.
5. Repeat the same process with other drives, type "d:" and do the same thing. then next "e:".and restart your computer.
6. Restart your computer and it's done. Enjoy the freedom to open hard drives on a double click.