So Santa left a brand-new computer under the tree this year, eh? Lucky you! If you\'re spending the holiday setting up a new Mac or PC, it\'s time to get filled with free software cheer. While the Lifehacker editors take today off to throw back some eggnog, you can point your clicker at a holiday feast of power tips and downloads. Trick out your new rig with our favorite system tweaks and downloads for Windows XP, Vista, Mac, and Linux.

Windows XP and Vista

• Top 10 Free Windows Downloads
  Our top picks of free Windows software downloads that will make your PC faster, stronger, more functional and productive.
• Power Replacements for Built-in Windows Utilities
  How many times have you wished Notepad had tabs, Paint supported layers, or Windows Explorer let you bookmark frequently used folders? Power users need power utilities, and Windows\' default system programs barely get the job done. Over time third-party developers have stepped up and built superior replacements to programs like Notepad, Paint, Windows Explorer, and the Command Prompt.
• Top Windows tweaks
  Hop in for a quick ride around Windows dialogs, tabs, menus, and toolbars to get your XP fitting like a glove.
• Windows Vista Power Tips
  After weeks of test-driving Windows Vista full-time, there are several tips and tweaks I wish I\'d known before I started.
• Top 10 Free Windows File Wranglers
  Windows Explorer and its weak band of file manipulation functions just don\'t cut the mustard for people with lots of data and only a little time, but several free utilities can help out.
• Automatically Load and Update Your Windows Systems
  One of the best parts of getting a new computer for the holidays—other than that new computer smell—is setting up a fresh, clean system exactly how you want it.

Mac

• A Guide to Switching to a Mac
  There\'s no need for you to waste your precious time figuring out the minutiae of a new operating system. To ease this transition for all of the new Mac owners out there, here\'s a quick guide for Mac newbies making the big switch.
• Build Your Mac with 20 Useful Downloads
  You\'ve got a new Mac running a fresh Leopard install, and now you\'ve got to load it up with all your essential software.
• Top 10 Mac OS X Tweaks
  Mac OS X is a great operating system out of the box, but a few simple customizations can make it even better. Ed: This guide was written regarding Tiger, but most of it will still apply to Leopard.
• Top 10 Mac Utilities
  The system utilities that add extra polish and convenience to your Mac\'s working environment. Most (but not all) of these little suckers are free, many live in your Mac\'s System Preferences pane and on the menubar, and all of them greatly enhance your overall Mac experience.
• The Complete Guide to Mac/Windows Interoperability
  Today Mac OS and Windows can work together in harmony on the same home network, sharing files and printers, mounting one another\'s drives and using the same equipment, like wireless routers and USB drives.

Linux

• Top 10 Ubuntu Applications
  While Ubuntu comes jacked with useful applications out of the box, there\'s a big selection of free, thriving Linux desktop software that matches or betters their Windows and Mac counterparts in terms of features.
• Power Up Your Linux Desktop With Compiz Fusion
  Not only can desktop decorator Compiz Fusion add eye candy to your system that leaves Windows and Mac users drooling on their keyboards, it can seriously boost your productivity.
• Top 10 Gnome Desktop Tweaks
  The desktop environment for many Linux users, Gnome, is fast, organized and very easy to learn. But Gnome is also very powerful and highly customizable.
• Slim Down and Speed Up Linux
  While Linux is pretty efficient with a computer\'s resources out of the box, there are still ways you can make it run leaner and meaner on your desktop.

Finally, if it was a widescreen monitor that you unwrapped today, find out how to make the most of your dual monitors, and de-smudge that new glossy screen.

A merry happy day to all of you, whatever you\'re celebrating. Back tomorrow!