[wpurdin]

I have a Compaq Presario, HP model SR5027CL with AMD Athlon 64 Processor 4000+, 2.6 Ghz, 894 MB memory and 32-bit OS. It has Windows Vista Home Premium. I had a lot of trouble with Norton 2008 slowing down the system, letting viruses in, turning off my firewall and not letting me download other antivirus programs. I had to do a system recovery and uninstall Norton. I then downloaded Mozilla Firefox, went online and got Avast, Threatfire, and Avira from download.com. Then I did the Windows update. One of the update files didn't download. I assume that was the Norton update. During the process, I read in a FAQ at the Avast site, that you should uninstall Norton before installing Avast. However, they also said that any other antivirus program may interfere with Avast and make Windows unstable. Is this true or are they just trying to keep you from comparing Avast with another program like Avira which might be better? I've read elsewhere that it's advisable to have two or more antivirus programs, as one program alone can't catch every virus. I didn't notice any problems after I downloaded the three programs. However, this morning, after I scheduled threatfire and Avira to do scans during the wee hours, my screen was blank and nothing appeared after several minutes. So I had to reboot. Now everything seems okay, my hard drive has plenty of room, the system's fast and apparently the scans didn't pick up anything. So I don't know.

A couple of other related questions: How often should I do scans? And should I keep my computer ON, in sleep mode or OFF at night?

Thanks

[rookie147]

I do not recommend that you have more than one antivirus product installed and running on your computer at a time.
The reason for this is that if both products have their automatic (Real-Time) protection switched on, then those products which do not encrypt the virus strings within them can cause other antivirus products to create "false alarms". It can also lead to a clash as both products fight for access to files which are opened again this is the resident/automatic protection.
In general terms, the two programs may conflict and cause false alarms - when the antivirus software tells you that your PC has a virus when it actually doesn't. Also it can cause system performance problems; your system may lock up due to both software products attempting to access the same file at the same time.
With regards to your second question, I would personally say that running a scan once a week (in Safe Mode) will suffice; of course the amount it based on how much time you have during which to run them.
Finally, whether you turn your computer off at night is completely up to you, it will not affect performance if you leave it on for long periods at a time - I know people who have never turned their computer off, often five years or so. Turning it off however will obviously save some energy ... and therefore decrease your electricity bill slightly.

[wpurdin]

In your opinion, which is better: Avast or Avira? Also, wasn't Threatfire designed to to be used with other antivirus programs and won't conflict because it doesn't try to access the same files but just analyzes behavior? Thanks for your advice.

[rookie147]

Yes, Threatfire was made to be used alongside another scanner, so this is the one exception where having this programme installed with another piece of antivirus software is acceptable.
I would personally have to say that Avast! is better; I have used it for many years without any problems. Once again, many people's opinions on this subject will differ and at the end of the day each person will have one which they prefer - not necessarily based on detection or protection, just because it feels right.

[Elvandil]

Having more than one is asking for trouble. They install driver-level components that can easily conflict.

Find a good one and stick with one.

[wpurdin]

I've decided to keep Avira and Threatfire and uninstall Avast. I based my decision on user reviews at download.com and the fact that Avast crashed my computer when I used it for a boot time scan. Thanks for the advice guys.

[Elvandil]

Sounds good.

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