Am I getting virus? I downloaded a anti-virus program
That will mess things up for certain. Whatever the problem is, it's not a virus, and an anti-virus problem is likely to make it worse.
Run Etrecheck and post its results in a reply:
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.
Right, and the reason your Mac became unresponsive can be number of different things that Etrecheck may help reveal. Etrecheck itself is harmless.
Make sure you have adequate backups because what you describe can be a symptom of an impending hard disk failure. There is not enough information to conclude that is the problem, but you should have backups anyway.
here is the result after using the Etrecheck. Most of them don't make sense to me, but hopefully you guys know what they are and what the problems are with my mac! thanks a lot!
iMac (21.5-inch, Mid 2011)
iMac - model: iMac12,1
1 2.5 GHz Intel Core i5 CPU: 4 cores
4 GB RAM
AMD Radeon HD 6750M - VRAM: 512 MB
Mac OS X 10.7.5 (11G63) - Uptime: 0 days 0:12:16
ST3500418AS disk0 : (500.11 GB)
disk0s1 (disk0s1) <not mounted>: 209.7 MB
Macintosh HD (disk0s2) /: 499.25 GB (457.98 GB free)
Recovery HD (disk0s3) <not mounted>: 650 MB
Apple Inc. BRCM2046 Hub
Apple Inc. Bluetooth USB Host Controller
Apple Inc. FaceTime HD Camera (Built-in)
Apple Internal Memory Card Reader
Apple Computer, Inc. IR Receiver
Apple, Inc. iMac
Problem System Launch Daemons:
[not loaded] ftp-proxy.plist
Problem System Launch Agents:
User Launch Agents:
User Login Items:
3rd Party Preference Panes:
User Internet Plug-ins:
Top Processes by CPU:
0% Activity Monitor
0% Microsoft Excel
Top Processes by Memory:
152 MB Google Chrome
135 MB mds
98 MB Microsoft Outlook
90 MB Finder
74 MB WindowServer
70 MB Dropbox
66 MB Microsoft Excel
45 MB UncleGravyRenewingAgent
45 MB Dock
37 MB Microsoft Database Daemon
Virtual Memory Statistics
1.26 GB Free RAM
1.37 GB Active RAM
584 MB Inactive RAM
807 MB Wired RAM
539 MB Page-ins
0 B Page-outs
Create a new, temporary account according to these instructions: Isolating an issue by using another user account
Log out of your normal account, log in to the temporary one, and test again.
For the purpose of testing don't use Chrome. Use Safari or Firefox instead. Determine if your slowdowns and crashes are mitigated while using the temporary account. If they are, then the problem lies with your account's User Login items, Internet plugins, Chrome, or all of these. If the problems persist, then you may have hard disk corruption that may be fixable with Disk Utility, or corruption in OS X that can be fixed by reinstalling Lion. Both of these options are available by starting your Mac using OS X Recovery.
Delete the temporary account when you are finished with it.
4 GB is not an abundant amount of memory. Purchasing more RAM is likely to be beneficial, but will only hide the symptoms of poorly written programs that don't use system resources efficiently. Chrome is a notorious resource hog that runs poorly on Macs.