Sometimes Putty’s default settings drives me insane.
The annoying system bell and invisible dark blue on black colour scheme suck. (My opinion)

Cool reference:
http://dag.wiee.rs/blog/content/improving-putty-settings-on-windows

In a nutshell:
Putty settings summary.
Category: Session
Connection type: SSH
Close window on exit: Never

Category: Terminal > Bell
Action to happen when a bell occurs: Visual bell (flash window)
Taskbar/caption indication: Flashing

Category: Window
Lines of scrollback: 20000
Reset scrollback on keypress: Checked
Reset scrollback on display activity: Unchecked

Category: Window > Appearance
Font: Lucida Console, 9-point
Font quality: ClearType
Gap between text and window edge: 3

Category: Window > Translation
Character set: UTF-8
Handling of line drawing characters: Unicode

Category: Window > Selection
Action of mouse buttons: xterm (Right extends, Middle pastes)
Paste to clipboard in RTF as well as plain text: enabled

Category: Window > Colours
ANSI Blue: Red:74 Green:74 Blue:255
ANSI Blue Bold: Red:140: Green:140 Blue:255

Category: Connection
Seconds between keepalives (0 to turn off): 25

Category: Connection > SSH > X11
Enable X11 forwarding: enabled