Have you checked activity monitor to see if there's a process thats hogging processor and/or ram? Whats the ratio of pageouts to pageins? How much total and free space do you have on your hard drive?
How to use Activity Monitor http://support.apple.com/kb/HT1342
Your confusing hard drive storage space with RAM (Random Access Memory)?
Click once on the icon of your main internal hard drive and use the key command Command-I and tell us how much hard drive specs is left on your iMac.
Before arbitrarily deleting items, you have the option of either burning your data to discs, Flash drives or purchasing an external hard drive and copying or cloning your important data there.
I would save the data rather than deleting it. You never know when you might have a need to recover old data files.
Here are some of my tips for deleting or archiving data off of your internal hard drive.
You'll need to free up lots of hard drive space.
At a minimum, at least, 15 to 20 GBs of space.
Perhaps even more.
Hard drive full or near full:
Have you emptied your iMac's Trash icon in the Dock?
If you use iPhoto, iPhoto has its own trash that needs to be emptied, also.
If you use Apple Mail app, Apple Mail also has its own trash area that needs to be emptied, too!
Other things you can do to gain space.
Delete any old or no longer needed emails and/or archive older emails you want to save.
Look through your Documents folder and delete any type of old useless type files like "Read Me" type files.
Again, archive or delete any old documents you no longer use or immediately need.
Uninstall apps that you no longer use. If the app has a dedicated uninstaller, use it to completely uninstall the app. If the app has no uninstaller, then just drag it to the OS X Trash icon and empty the Trash.
Also, if you save old downloaded .dmg application installer files, you can either archive and delete these or just delete the ones you think you'll never install, again.
If you can still find this app, download and install Monolingual.
This app will delete all other OS X languages that you do not need or use on your iMac.
You can check the languages that you want Monolingual to delete and uncheck others you wish to keep.
Download an app called OnyX for your version of OS X.
When you install and launch it, let it do its thing initially, then go to the cleaning and maintenance tabs and run all of the processes in the tabs. Let OnyX clean out all web browser cache files, web browser histories, system cache files, delete old error log files.
Typically, iTunes and iPhoto libraries are the biggest users of HD space.
If you have any other large folders of personal data or projects, these should be thinned out, moved, also, to the external hard drive and then either archived to disc and/or deleted off your internal hard drive.
You may have to Purchase an external FireWire or Thunderbolt hard drive to move these files/data off of your internal drive to the external hard drive and deleted off of the internal hard drive.
If you can still find this app, download and install Monolingual.
Deleting localization files is an act of desperation. They do not occupy a significant amount of space.
Monolingual has been known to break application updates such as those for Microsoft Office, and there is no way to "undo" the system modifications Monolingual is capable of doing short of reinstalling OS X.
Rather than ask a dozen questions for more details about the problem consider the following:
Apple Support Communities contributor etresoft wrote a very useful app to quickly gather certain system information that may help point to a cause of this problem. Go to his website, download and run EtreCheck:
Etrecheck will be in your Downloads folder. Open it from there. You may see the following dialog box:
Click Open - etresoft contributes to this forum frequently and can be considered a trustworthy developer.
It will take a moment to run as it collects its data.
Copy and paste its output in a reply.
Do not be concerned about anything that says "Problem" or "failed".
EtreCheck was designed to remove any personal information (such as your computer's name and serial numbers) but if you see anything that looks like an email address or any other personal information that should not be divulged to others, please delete or obscure that information when you post the reply.
When you are finished with EtreCheck, quit the program. It occupies very little space, and you can keep it or drag it to the Trash as you wish.
iMac - model: iMac11,2
1 3.2 GHz Intel Core i3 CPU: 2 cores
4 GB RAM
ATI Radeon HD 5670 - VRAM: 512 MB
Mac OS X 10.7.5 (11G63) - Uptime: 1 day 11:39
ST31000528AS disk0 : (1 TB)
disk0s1 (disk0s1) <not mounted>: 209.7 MB
Macintosh HD (disk0s2) /: 939 GB (684.87 GB free)
Recovery HD (disk0s3) <not mounted>: 650 MB
asdf (disk0s4) /Volumes/asdf: 60.21 GB (60.05 GB free)
OPTIARC DVD RW AD-5680H
hp deskjet 5100
Apple Inc. BRCM2046 Hub
Apple Inc. Bluetooth USB Host Controller
Apple Internal Memory Card Reader
Seagate Backup+ Desk 2 TB
disk1s1 (disk1s1) <not mounted>: 32 KB
Seagate Backup Plus Drive (disk1s3) /Volumes/Seagate Backup Plus Drive: 2 TB (1.55 TB free)
Apple Inc. Built-in iSight
Apple Computer, Inc. IR Receiver
com.seagate.driver.PowSecDriverCore Version: 5.2.3
com.seagate.driver.PowSecLeafDriver_10_5 Version: 5.2.3
Problem System Launch Daemons:
[not loaded] ftp-proxy.plist
Problem System Launch Agents:
[not loaded] com.adobe.AAM.Updater-1.0.plist
User Launch Agents:
User Login Items:
3rd Party Preference Panes:
Akamai NetSession Preferences
User Internet Plug-ins:
Top Processes by CPU:
Top Processes by Memory:
618 MB HP_Deskjet_F4400_series
385 MB WebProcess
127 MB Safari
57 MB WindowServer
53 MB Finder
49 MB mds
37 MB loginwindow
29 MB SystemUIServer
25 MB PluginProcess
25 MB Dock
Downloading torrents opens up the proverbial can of worms. No one can begin to guess what may have been occurred as a result.
Disconnect your external Seagate disk drive and see if that makes a difference. The system modifications it installed should not be necessary to use it as a backup disk. Other than that, the uncertainty of malware intrusion as a result of downloading torrents makes troubleshooting problematic. Also, consider creating a temporary User account to determine if the problems continue after logging out of your usual account, and logging in to the temporary one. If the system behaves normally under that account, your problems may be fixable short of erasing everything and reinstalling OS X.
To create a temporary account to isolate user-specific problems: Isolating an issue by using another user account
Delete the temporary account when you are finished troubleshooting.