Why has my iMac gotten slower for the past few months? My iMac has gotten slow lately. The (wireless) keyboard lags if I type while a program or dialog box is opening. A couple of Chrome tabs crash every day. A few days ago, Preview and TextEdit started crashing on open. Finder sometimes takes over seconds to come up when I click it in the dock. TextEdit sometimes takes ten seconds to launch, sometimes takes two.

Info dump:

I have an iMac from 2007, upgraded a year ago by a third-party vendor, currently with these specs:


Processor: 2.8 GHz Intel Core 2 Duo
RAM: 2 GB 667 MHz DDR2 SDRAM
Graphics: ATI Radeon HD 2600 Pro 256 MB
HD: 1 TB ATA Disk (466.76 GB free)
Backup drive (nightly 4:30 AM backups with SuperDuper): External 1 TB USB Disk (479.21 GB free)
OS: Lion


I usually concurrently use:


Adium
Google Chrome (often six to twelve tabs open)
iTunes


On top of that, I often open one to three of these apps:


Pixelmator
Photoshop
TextEdit
The Hit List
Word
The official Twitter app
Transmission


My menu items include:


Textexpander
Last.fm scrobbler
Dropbox
Flux
iStat Menus


My active Chrome extensions are:


Adblock Plus
Add Facebook Events to Google Calendar
Better Gmail
Clickable Links
Clip to Evernote
Google Calendar Checker
Google Mail Checker
Google Reader RSS Subscriber
History Calendar
Hover Zoom
Instachrome
Logitech Device Detection
Missing e
Page One
Read WSJ Extension
Reddit - display user link titles
Reddit Companion
Reddit Enhancement Suite
Search by Image (Google)
Speeddial 2
StumbleUpon
Turntable Scrobble


I have about a dozen disabled extensions.

Here's a screenshot of Activity Monitor with Chrome (three tabs), iTunes, Adium, Hit List, Activity Monitor and Word open.

The top of the computer is uncomfortably hot to the touch. I tried tracking the system temperature with iStat Menus, and it reported 50° C and lower.

What's making my computer so slow? Too many Chrome extensions? Not enough RAM? Dusty insides?

My MacBook Pro, on which I do the same work, run the same apps (though usually not iTunes) and the same Chrome extensions, behaves much faster. It has 4 GB 1067 MHz DDR3 RAM and a 2.66 GHz Intel Core 2 Duo processor.
Here's a few things I would try:


Do basic system maintenance (repair permissions, clean caches, run daily-weekly-monthly maintenance scripts). I like ONYX (http://bit.ly/eCzYfj) for doing this, but there are plenty of other options that do the same thing.
Make sure you have at least 20% free disk space. If not, try clean up and free some space.
If things are still slow, try creating a new user account and logging in with that. If that account runs much better you still have some cleanup to do.
Check your login items (in system preferences, User &amp; Groups). If there are login items you don't recognize/need try disabling them.


I would also look into investing in at least a 2MB memory upgrade. Not too expensive and it looks like you could use it.

Good luck...