My late-2009 21.5-inch iMac is freezing so much, it's basically unusable.

Question

About 2 weeks ago, I started to see a slow decline in overall speed. Now, my iMac is so slow, and freezes up so much, that I basically can't use it. I have ran the Apple hardware test that came with my mac on a CD, checked to make sure I wasn't using too much RAM when the freezing happens, verified the disk image, and it all came out normal. I've also tried creating a new user, and that had no effect. However, I have noticed that periodically (maybe once every week) I see a small window pop-up and disappear almost immediately. Today, I was finally able to see what the title bar said on the little window. It said easyNAT. I googled this, and it's some kind of 3D modeling software by a company named bionatics. I've never downloaded anything like that. Could this be the problem? How do I fix it? If this isn't the problem, what do you recommend I do? I was planning on taking it to the Apple store this weekend, but it would be preferred if I could fix it myself. I haven't downloaded anything or done anything different with my mac since I started seeing the slow-down. One thing I did notice is that it started to do the freezing thing in safari, and slowly spread to the rest of my applications, and eventually the finder. Also, whenever I try to download the beta 2 for the iPad (I'm a developer), It will finish downloading, and when I try to open the disk image, it will try to verify it FOREVER and eventually say something along the lines of error:input/output and not open it. Could it be a virus? Sorry I've been rambling for so long. I'm trying to give as much info as possible, so I can get this fixed. Thanks for your help in advance.

Answer 1

Now, my iMac is so slow, and freezes up so much, that I basically can't use it.
If you have any peripherals connected to your computer, disconnect them. iMac still slow and freezes up?
How large is your hard drive and how much space do you have left.
Disconnect all peripherals from your computer. Boot from your install disc & run _*Repair Disk*_ from the utility menu. To use the Install Mac OS X disc, insert the disc, and restart your computer while holding down the C key as it starts up.
Select your language.
Once on the desktop, select Utility in the menu bar.
Select *Disk Utility.*
Select the disk or volume in the list of disks and volumes, and then click *First Aid.*
Click _*Repair Disk.*_
Restart your computer when done.
Repair permissions after you reach the desktop-http://docs.info.apple.com/article.html?artnum=25751
easyNAT thing I talked about earlier showed up in the processes, but it took up 0% of the CPU. *I still have absolutely no idea what that is.*
It's also a plug-in. Spotlight search your hard drive for easyNAT. If you download Find File or Easyfind, your search will be made easier. Both utilites can be found at Macupdate.
I've never downloaded anything like that
Anybody uses your computer besides yourself?
I was planning on taking it to the Apple store this weekend, but it would be preferred if I could fix it myself.
If you have Apple Care, give them a call. Let them do what you paid all that money for them to do.
If your iMac is still under its one year warranty, take full advantage of it before it runs out. Especially, if you do not have Apple Care.
Could it be a virus?
No. There are no viruses for os x.
Sorry I've been rambling for so long.
Rambling is good. The more details we have from you the easier it is to help with troubleshooting. So speaking for myself, thank you for rambing.