You can intentionally hide a computer from the browse list by using tip 0043.

You can accidentally hide a computer from the browse list by manually setting srvcomment to more than 48 characters.

Use Regedt32 to navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters

Double click srvcomment in the right hand pane and shorten the description so it does not exceed 48 characters.

Shutdown and restart your computer.