If you don't have virus/spyware protection, download some free software NOW. Not only does it slow down your computer, but it can kill it as well. I actually suffered from a computer not booting up because it has taken a shit load of a beating from viruses and spyware that infected it. If I hadn't backed up the NG image archive (I put them in the school's network drive... yeah not a good idea but it saved my ass), I would have lost 1/3 of the image archive (of what I have right now). I'm sure I lost a small fraction of it, but whatever that's the past.
In fact, today when I booted Ustream Producer this computer had shut down mysteriously, and wouldn't boot up until 40 seconds later. And it took a lot of ass-kicking to get it booted. That's when I decided to scan this thing to clean it up and improve performance. Here's how:
For (free) Spyware protection, I recommend Spybot - Search & Destroy. For the first time since I installed it this thing detected like 60 alerts in my computer (and I had NO protection BTW, and I use this computer 99% on NG so that just says how dangerous outside websites and software can be). I deleted all of them, and this damn thing is running 50x faster than before. In fact, I think it will take less time to complete image archive stuff than usual (still not as fast as that $3,000 laptop I posted on SMBS).
I'm still yet to install anti-virus, so I can't give an opinion yet nor on what I recommend to install. But seeing how much spyware shit I got, I wouldn't be impressed on how many viruses I have as well.
Also, defragment your hard drive occasionally (like once every 2 weeks). This will also speed up your computer. All defragmenting does is gathers all the particles of all the files in your computer (yeah your files are scattered all over your hard drive - they are not grouped together like you would expect, so a single word document could have 20 particles all over the hard drive) and puts them together. If you don't defragment your hard drive, your computer has to work hard to find all the particles to open up a file.
Also if you do defragment your hard drive do it TWICE (this is important). Doing it once won't do much good. The first time your computer will gather the particles but won't put them in the right place. The second time it will put them in order correctly. Credit to Basset for telling me that.
Open discussion post.
thenewbies
When it comes to antivirus, NOD32 and Kaspersky would probably be your best bets. High detect rates, low impact, etc. The best free AV would have to be avast. It's name is a pirate reference, so it's made extra awesome. It contains a surprisingly complete suite for free software. And it's also very good stat-wise.
Some defrag programs will organize and arrange files, so in some cases, there's no need to do it twice. Some defrag programs don't even bother with fragment arrangement, so doing it twice might not really help that much.
A nice fast defrag app is Auslogics Defrag. It's really fast at its job, too, takes a tiny fraction of the Windows default defrag's time, and does a bit more too. A bit heavy on nagware, though. A nice, thorough defragger would be jkdefrag. It has a lot of options for you to choose from, like how to arrange data, the depth of defragging, lots of crazy shit, though it lacks a good UI.
Back up. Take this as a warning, kids.
NGReviewEater
I have Avast downloaded, and my dad has some other anti-virus in his fast computer.
Personally I never really defragment my drive since the computer does it itself, but the bottom line is defragmenting the drive makes it faster.
Oh yeah I have backed up all of my stuff. In fact, I'm ready if this computer dies (which it shouldn't).