Some questions from a still learning Mac user

[NewJeffCT]

cross-posted from the Lounge, where I usually get more response.

My iMac is less than two years old, but is much, much slower than it was when we first bought it. A few months back, somebody suggested updating the permissions, which I did, but that was no help at all. I was in the apple store last night and saw something that allows you to run a defrag and a scan disk/surface scan for your mac. Is that something useful? I had to run, so did not get a chance to ask the people in the store. I know when I used windows before, I would run those apps regularly, but I don't see those apps built into my iMac. (I did do a search on "defrag" but it came up with some weird spanish language PDF file as the only result)

Also, sometimes, if I am in the process of clicking on a file or application on my desktop, the file icon will become all pixelated lines instead of the picture of the application or file...Also, nearly every time I use my iMac now, the picture on the screen collapses and becomes all scrunched up and barely readable - not pixelated, like with the file icons. I can reboot the computer and it's okay for a little while, but it then starts up again. It almost sounds like some sort of virus.

Also, I'm still getting the "secure download" from Safari for emails with attachments.

Any ideas?

[Poiuyt]

1. I would try a disk maintanence program

Something like Onyx or Yasu (both free) will clean out your cache and history, repair permissions, etc. That's what's most likely causing the slowdown on your computer. I run one of them once a week to keep my iMac from bogging down. Also, make sure your hard drive has plenty of free space. OS X needs room. Your computer will slow down if the HD is more than 70-80% full.

I'm not sure about your second problem. It's not a virus, but something got corrupted. I'm not sure I understand what's happening. What picture on the screen is becoming scrunched up? In any event, I would run DiskWarrior. It's a disk repair program that always seems to solve whatever is ailing your Mac. It's well worth the cost.

[NewJeffCT]

2. Thanks

My hard drive is not even close to 50% full, let alone 70%

[Omphaloskepsis]

3. OS X will auto-defrag any file over 20 megs.

You don't need to pay for software to do it. Have you tried a "Archive and Install"? Basically you boot from the CD/DVD your computer came with and it saves your old System Folder and puts in a fresh copy. You can put back what you need when you are done.

And if you want to speed up your machine get more RAM. OS X gobbles it up. It is a cheap way to get drastic speed improvements.

And the Safari problem is a Yahoo Mail thing. The problem is on their end.

[NewJeffCT]

4. I'm pretty sure I don't have any individual files that are over 20 mb

but, we probably together, we have over 20mb of files on the computer.

[Richard Steele]

5. Another FANTASTIC free "disk maintenence" application...

...is "Applejack". It's an app that was recommended to me
by someone here in the DU Apple Group (I forget who, sorry)
and I really love it. It solved some issues that the Apple
Disk Utilities (and a commercial product which shall remain nameless) didn't,
and I haven't needed anything else since I started using it:

Check it out HERE: http://applejack.sourceforge.net/

[alfredo]

6. Mac Janitor is good too. Don't clutter your desktop with

folders. That will slow down the computer.

[ChairmanAgnostic]

7. Your cache is probably filled as well. Cache Out is shareware

that cleans it out. A great program. use it daily.