- Do a fresh install. Find the OS install disc (if your system came with one) not a restore disc, but the original Windows install disc. If your system did not come with an original Windows 7 disc than try out PC Decrapifier This is all in effort to remove any of the nagware, crapware, or any unwanted manufacturer pre-installed program. Cuz there's nothing like buying a new system only to have it run slowly.
- Get updated. Run Windows Update and get all the latest drivers and updated for Windows.
- Get protected. After you've done Windows Update go and get a copy of Microsoft Security Essentials. Security Essentials is a lightweight, unintuitive, no nonsense anti-virus.
- Install what you want. Ninite.com creates a customized automatic installer for unattended bulk installation for many of the most popular open source software. Some of what I recommend is Chrome, VLC, Picasa, OpenOffice, SumatraPDF, Dropbox, KeePass, Malwarebytes, ImgBurn, uTorrent, 7-Zip
- Back it up. Once your updated and got everything installed the way you want, go grab and install a copy of Macrium Reflect and create your own restore image. So if something goes bad...crash, virus, corruption etc... you can quickly get back to a good starting point. and always, always have your personal files, pictures, music, bookmarks, account data files and anything you cannot afford to lose backed up to multiple separate locations. Dropbox is a great tool for providing off site "cloud" like redundancy, but at the very least have an external drive that mirrors the files using something like SyncToy.
Written while watching Tekzilla Top 5 Tips For A New PC. so it's a basic transcript.