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I have an anti-virus program running for several hours and the only way to keep it going is to disable the sleep mode. I also have Windows 7 through VMware, and the virus program checks this OS in particular for virus problems.

I have been able to disable the Mac screen saver but not the Mac sleep mode.
I'm not sure if this can be done, and as a result, the virus program stops working when the computer is in sleep mode.
 
I've found it now.
It's under Energy Saver in System Preferences.
 
Ah, I misunderstood.
Btw:
There are currently no viruses for Mac OS X in public circulation, only a handful of trojans and other malware, which have to be installed manually via entering the administrator password.
The only anti-virus you need to protect your Mac is education and common sense.

Mac Virus/Malware Info
 
I've found it now.
It's under Energy Saver in System Preferences.
You can use Caffeine to temporarily override your Energy Saver settings, with a single mouse click. And as has already been stated, you don't need anti-virus software to protect your Mac from malware. Read the Virus/Malware link that simsaladimbamba posted.
 
Go to "System Preferences -> Energy Saver" and slide the computer sleep slider to "Never". The system should now never go to sleep unless you tell it to.
 
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