Changing the timeout of the tooltips (or disable them)

If you would like to change to timeout of the tooltips, you'll have to change the value of the DWORD BalloonTip in the key [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
\Explorer\TrayNotify]
Setting it to 0000001E will change the timeout to 30 seconds.
You don't feel comfortable changing this value yourself? Download the regfile here.

If you would like to disable the tooltips, change the value of the DWORD ShowInfoTip in the key [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
\Explorer\Advanced] to 0.
But you'll still have tooltips for the minimize, maximize and close buttons. Those can be disabled in the key [HKEY_CURRENT_USER\Control Panel\Desktop\]. In Windows 9x you'll have the key UserPreferenceMask, in more recent versions it's named UserPreferencesMask.
Default the value of this key is "BE 00 00 00". In this case, you can change it to "3E 00 00 00".
If your key has another value, you can calculate the new value by substracting "80 00 00 00" in Hex. You can do this easily using the Windows Calculator (in Scientific View and Hex mode).

A little example:
If your key is 9E3E0080, just substract 8000000, the result is 1E3E0080

There's some more explanation on this key at http://www.virtualplastic.net/html/desk_reg.html#mask