Viruses and trojans, malware and bloatware. Let’s face it, the Internet is more dangerous and contagious than Van Wilder’s bedroom. Your computer, if it’s a PC, likely came with some trial-version of a mainstream anti-virus solution such as Norton Internet Security or McAfee Internet Security.

Here’s the problem: those trials are going to expire and ask you to plant a few more dollars in that graveyard called your computer. Never fear, here are four free applications that will make your computer (and you) happier and healthier.

1. Windows Security Essentials: Go to Microsoft’s Web site and download Windows Security Essentials. It’s a lightweight anti-virus with a user-friendly user interface (UI) that requires little setup. It updates automatically and stays out of the way.

2. Malware Bytes: Sometimes, an anti-virus isn’t enough to catch all the spyware and malware that passes through your inbox. For that, download Malware Bytes, software specifically designed to catch and contain those nasty bits. In April 2009, the program received CNET’s Editor’s Choice Award. The site does offer a premium package, but the free version should be more than enough.

3. PC-Decrapifier: Have you ever bought a computer only to have the desktop loaded with icons for free-trials or picture programs you never plan on using? Rather than going to Windows’ stock uninstaller to manually remove each one, let this program do it all for you. Simply run the program, select what you don’t want, and let it take care of the rest.

4. CCleaner: Windows Temporary Files, Cookies, Registry clutter, this program handles it all. This app analyzes the data on your computer and lets you know what it thinks you should delete. CCleaner is a great way to clear out browser data all in one spot. The program also searches the Windows Registry for redundant entries. Caution: Take care when deleting the registry and always follow the CCleaner’s on-screen prompt for a backup of registry data.