My Mac is running VERY SLOW

There aren't any Mac viruses but check for malware just in case.

Follow the instructions from the first two links.

http://www.fixkb.com/2011/05/remove-mac-protector.html

http://www.macrumors.com/2011/05/02/new-macdefender-malware-threat-for-mac-os-x/

And read here. http://www.reedcorner.net/guides/macvirus/

And check the startup disk as it may need repairing.

Using Disk Utility to verify or repair disks

For Safari. http://support.apple.com/kb/TS3230?viewlocale=en_US

In addition, more importantly, check your login items (the things that start when you first turn on your machine).

got to: Prefs > Accounts > Login Items

If too many things &/or items that look weird are in there, remove &/or report back here.

(it is a very good idea to attach a screen capture of the prefs for this: see the camera icon in the tool bar ^above^ when adding/editing posts.)

Kappy's Personal Suggestions for OS X Maintenance

For disk repairs use Disk Utility. For situations DU cannot handle the best third-party utilities are: Disk Warrior; DW only fixes problems with the disk directory, but most disk problems are caused by directory corruption; Disk Warrior 4.x is now Intel Mac compatible. TechTool Pro provides additional repair options including file repair and recovery, system diagnostics, and disk defragmentation. TechTool Pro 4.5.1 or higher are Intel Mac compatible; Drive Genius is similar to TechTool Pro in terms of the various repair services provided. Versions 1.5.1 or later are Intel Mac compatible.

OS X performs certain maintenance functions that are scheduled to occur on a daily, weekly, or monthly period. The maintenance scripts run in the early AM only if the computer is turned on 24/7 (no sleep.) If this isn't the case, then an excellent solution is to download and install a shareware utility such as Macaroni, JAW PseudoAnacron, or Anacron that will automate the maintenance activity regardless of whether the computer is turned off or asleep. Dependence upon third-party utilities to run the periodic maintenance scripts had been significantly reduced in Tiger and Leopard. These utilities have limited or no functionality with Snow Leopard and should not be installed.

OS X automatically defragments files less than 20 MBs in size, so unless you have a disk full of very large files there's little need for defragmenting the hard drive. As for virus protection there are few if any such animals affecting OS X. You can protect the computer easily using the freeware Open Source virus protection software ClamXAV. Personally I would avoid most commercial anti-virus software because of their potential for causing problems.

I would also recommend downloading the shareware utility TinkerTool System that you can use for periodic maintenance such as removing old logfiles and archives, clearing caches, etc. Other utilities are also available such as Onyx, Leopard Cache Cleaner, CockTail, and Xupport, for example.

For emergency repairs install the freeware utility Applejack. If you cannot start up in OS X, you may be able to start in single-user mode from which you can run Applejack to do a whole set of repair and maintenance routines from the commandline. Note that AppleJack 1.5 is required for Leopard. AppleJack 1.6 is compatible with Snow Leopard.

When you install any new system software or updates be sure to repair the hard drive and permissions beforehand. I also recommend booting into safe mode before doing system software updates.

Get an external Firewire drive at least equal in size to the internal hard drive and make (and maintain) a bootable clone/backup. You can make a bootable clone using the Restore option of Disk Utility. You can also make and maintain clones with good backup software. My personal recommendations are (order is not significant):

Backuplist

Carbon Copy Cloner

Data Backup

Deja Vu

iBackup

JaBack

Silver Keeper

MimMac

Retrospect

Super Flexible File Synchronizer

SuperDuper!

Synchronize Pro! X

SyncTwoFolders

Synk Pro

Synk Standard

Tri-Backup

Visit The XLab FAQs and read the FAQs on maintenance, optimization, virus protection, and backup and restore.

Additional suggestions will be found in Mac Maintenance Quick Assist.

Referenced software can be found at CNet Downloads or MacUpdate.

If you are noticing many colored beachball cursors then check out the FAQ for the SBBOD at the XLabs link above.

Open Activity Monitor in the Utilities folder. Select All Processes from the Processes dropdown menu. Click twice on the CPU% column header to display in descending order. If you find a process using a large amount of CPU time, then select the process and click on the Quit icon in the toolbar. Click on the Force Quit button to kill the process. See if that helps. Be sure to note the name of the runaway process so you can track down the cause of the problem.

There are no Mac viruses. Mac trojans do exist, but it would be very obvious if you had one of those. A "virus" should be the last thing you suspect when you have a problem, not the first.

Try the easiest thing first: Intel-based Macs: Resetting the System Management Controller (SMC)

If that doesn't help, try this: Mac OS X: Starting up in Safe Mode

Some things don't work in safe mode, but you should be able to do enough to determine whether the problem still exists. If it goes away in safe mode, some third-party software you installed is the cause.

If the problem persists in safe mode after an SMC reset, then you should verify your startup volume in Disk Utility and reinstall Mac OS X from your installation DVD. Back up all data first.

In the time it takes to troubleshoot, you could erase and reinstall the Mac OS X providing all of your important files are backed up first.

10.6: Erasing and reinstalling Mac OS X on your startup disk

😎 and thanks for awarding points!