It's highly recommended to protect your computer against Virus, Malware, Spyware and other potential threats. Microsoft Security Essentials is one of the better, free solutions.
If any file can not be deleted, then you can use the program LockHunter, which removes the active connections of other applications to that file, which allow you to change or delete file.
Nice little program that enables you to close all your opened applications and windows with one single click. It works in Windows XP and Windows 7 and doesn't need installing.
RawTherapee is a free open source application for opening and editing RAW image files. It works on all major operating systems such as Windows, Linux and Mac OS X.
Pixlr is a free and probably the best web based image editor. I will show you how to open and and resize an image, I'm sure you will be impressed how well the web app actually works.
If you are a heavy twitter use, possibly with more then one account, than I suggest you to give Tweetdeck a try. You can arrange, schedule, monitor and manage your tweets with ease.
If you want to put your video files online using HTML5 then it's recommended to have three different formats for a full browser support. Those formats are mp4, ogv and webm.
