Protect your Computer
There's some free anti virus programs out there like AVG and Avast! and Windows Security Essentials, there's also ones you pay for like Norton, McAfee, and F-Secure. I use the latter. If you are a student, chances are your school will provide either a free or a discounted anti virus program. If not, perhaps you can get a deal through work. Keep in mind that the free anti virus programs may need to be used together, with programs like Malwarebytes and Spybot.
List of Windows 7/Vista/XP security software
The risk of losing everything on your computer is not huge. However, what if it were to happen? What if you lost all your home photos and videos? Maybe you have school work, or business work, on your PC. It's probably not worth risking.
One option you have is to use online backups. There are "cloud" services that offer online storage. You can always upload your photos to somewhere like photobucket, but it's probably faster and easier to just maintain your own personal backups.
Info for Windows 7 users: Backup and Restore
Another great feature is Restore Points. These are backups of only critical items like your registry, so they aren't huge files, and they save every time you install something new. In this way if you find suddenly your PC is acting weird, you can restore it to a point maybe a few days or a couple weeks earlier, when it was still fine.
Hard Drive Maintenance
At least on a monthly basis run a Disk Defrag program. Windows comes with one by default, but according to a fairly thorough benchmarker, MyDefrag appears to be one of the best. After you delete a few items of your computer, it will leave empty spots on your HDD. Eventually you'll install something else, and pieces of it will get stored in all these different locations. This means accessing a fragmented file can take a long time, because instead of a fast sequential read, it will be more of a random read as the head needs to constantly move around to read each little piece of the file. Note that HDDs are built to run for millions of hours, a defrag operation isn't any worse than what happens when it is fragmented, and shouldn't impact HDD longevity. There is a sidenote: this is not applicable to Solid State Drives, which should never be defraged.
A great review on the Impact of Disk Fragmentation
Another important thing to do at least every few months is to run a scan disk. Once you set it, you will need to reboot and then it will scan your HDD after the intial boot screens. What scan disk does, is it looks for sector errors on the HDD and either recovers them or essentially "removes" them so that data isn't put into a bad sector. Sometimes a bad sector can cause a lot of stability issues. Scan Disk is found in your System Tools (Start Menu > Programs > Accessories > System Tools. Please be aware, if you start getting bad sectors, the problem usually will get worse and worse until your drive is completely useless. If this is the case, please go get a new HDD.
Clean your System
You should consider deleting and uninstalling anything you don't use regularily. If you have a huge amount of photos and videos, consider burning them to a DVD or external drive and free up HDD room. This can also help improve performance, as HDDs slow down the more full they are.
Windows registry is a vital part to a stable PC. It contains key values for every single thing installed on your PC, and then some. It is in many ways at the very core of your PC's performance and stability. Eventually, a registry will get full of clutter. I use a program called CCleaner to keep my registry free of junk. This program is also good for finding other clutter on the HDD, like temp files. You shouldn't clean your registry all the time, but even every other month is good. Keep in mind that this can cause issues, too, so please at the very least make sure you're backed up and also save the registry before cleaning (via the prompt).
You can also go into your System Tools and run the Disk Cleaner which can find some of the junk left over. For example if you install a Windows Service Pack, you might have a couple hundred megabytes occupied by a "ghost image". Essentially this is a redundant backup - you may wish to keep it for a couple weeks after updating to a service pack, but otherwise it's just taking up space.
I would also suggest if you need to reinstall a program, do what you can to uninstall the old one/old version and remove it from your system. Sometimes left over traces of a program can really mess with a new install. With regards to graphics drivers, see yesterday's post.
Some programs, when uninstalled, like to leave traces outside of the registry - traces that use up sometimes precious hard drive space. You can manually hunt these down, typicall within the install location as well as in C:\Users\yourname\AppData or under C:\ProgramData - both of these files are typically hidden. An easy way to find them is to run a search. Alternatively, a program like Revo Uninstaller can be extremely useful.
Clean your PC
CPU coolers and graphics cards have fans and heat sinks, which are very prone to clogging with dust. If the heat sinks get clogged, the cooling performance is greatly reduced and you end up over heating. I've personally killed a graphics card this way, and it's pretty common for people to neglect this simple thing.
To clean the inside of your PC you'll ideally use a compressed air duster. Simply blast away the dust. You'll need to be careful when blasting the CPU and GPU coolers, because you don't want the fans to spin up or they actually create a voltage. If a heat sink is especially clogged, you may want to use an old toothbrush. You should not use a vacuum directly on PC hardware because it can generate a large electro static charge, and if it discharges into your PC it can break hardware. You can keep a vacuum nearby to suck up the dust, just don't let any bare metal touch the PC. If it is very dusty, you might want to just take the PC outside where you won't need to worry about the dust kicking up. Also, if very dirty, you may have to remove parts from the PC, including taking fans off the heat sinks, to really get it clean. To avoid all this hassle, just clean it out more often.
This is just touching the surface, I'll be writing a few more maintenance posts in the future, the next one will have to do with keeping system performance up.