Your Motherboard is not a bad board however it is very limited in running overclock settings, this being the case I can tell it is causing your graphics card and CPU slow downs on the hardware side even running at stock speeds.
I used to own a A7V8X and in fact my wife's computer with an XP2800+ still uses it.
Ok down to business!! All games use 100% CPU usage they have for some time now it's just how it works to keep it simple.
If you are looking for that frag in online games then the problem with the computer freezing is a bandwidth problem and partly because the A7V8X motherboard you have has 2 drawbacks.
The first problem is that it is 8X AGP BUSS and that would be great if we were all still using graphics cards with less then 128MB at 8X AGP but your card is faster then the A7V8X can handle when matched with a Cable or DSL online connection.
Here is what is happening to you.
When your online for various reasons the connection PINGS in game fluctuate up and down and this causes extra stress on the CPU to keep up with your bandwidth, combined with the AGP high end graphics card you have Hogging the AGP buss for Bandwidth your system is actually drowning it's self.
Solution.
You need to get your bandwidth speeds down on your internet connection. try setting your NIC card Network or onboard LAN to a lower connection speed like Full 10 Duplex. Your NIC is proly default set to Full Autonegotion allowing all your bandwidth to constantly slam into the CPU.
The second thing you can do is to Purchase a A7N8X Deluxe ver2.0 Motherboard the prices are well under $80.00 Can so lower in the U.S I am sure.
This board has 2 built in Network devices one is the 3COM standard Internet LAN or Network card this is a good RJ45 connection but not as well planned out for gamers as the BUILT IN Nvidia nForce MCP Networking RJ45 connection. With the Nvidia NIC or network card you have the option to set the driver to 2 setting one is All available bandwidth and the other OPTION lets you set the NIC to CPU man that is very nice and thought of I am sure by Nvidia for the gamers out there.
Setting the NIC card to CPU only allows enough bandwidth to keep your connection stable and fast as your CPU or lets encompass the whole computer by saying the connection speeds can no longer drown out the computers bandwidth allowing the AGP buss and CPU to communicate without getting drowned out by resource hungry connection packets.
Using the CPU load level choke on the Network card will prevent those computer freezes in game. The freeze happens when the CPU and AGP buss grab a breath trying to compute all the DATA and from your end it looks like a freeze of the game screen. In computer time anything that we can see that takes that long is an ICE-AGE event within the computer. Not good for the computer or hardware at all.
Your current RAM and Graphics card as well as your CPU will transplant very nicely into the new A7N8X Deluxe ver2.0 Motherboard.
Now if you are only gamming at home and not online unlikely since you said you were hunting for possible Trojan and viruses you will still get game freezes with the AGP Buss of the A7V8X motherboard and the XP3000+ Cpu that would be much better off in the A7N8X Deluxe ver2.0 Motherboard. I still use the A7V8X in my wife's computer but she only has a XP2800+ and it is running at 200MHz Memory speeds and a CPU speed of 2.0 just under 2.1 MHz.
If you are using the Steam Network to online game get used to Viruses Trojans and Bogus Registry keys as well as server side or hacker modified config folders. Hackers hack good players right through the game server right through the Steam Network.
Get a good fire wall set it to the Highest level this can also cause split second game freezing.............Now get your self a good IP scanner like COMMVIEW when you are in a game in Steam hit the windows key and go to the desktop and open COMMVIEW \Start it and watch the IP's that come in if you got your fire wall set-up correctly you should see a couple IP's from your ISP and ONE IP from the game server you are on.
The trick here is to see if a hacker is trying to mess up your connection times or hack into your computer when you are in game. Look at the game server IP number you are on if it has one port, Example [27015] and just that port you are ok but if you see that port, Example 27015,137,344 <---With 2 known Trojan ports or any other port hanging off the back of the server port you can bet your last Beer that some connectivity hacker is trying to access your computer piggybacking over the server IP number.
Make a fire wall rule allowing the Server IP on port 27015 this will allow you to play on that Server IP under that port. Now make another fire wall rule and this one is important and never thought of. Make a new rule Denying that Server IP but only for ports 137,344. What this does is it will block that Server IP but only on the ports specified in the example, or whatever port you see hiding behind the real server port.
I have used this for some time now and server in the game list that I ping at 80 ping then I go into the game fluctuate between 80 and 4 or 500 ping I use this approach to blocking the tag-on ports then my pings drop back to 80 ping and stay there.
I believe many Admin's online use third party chat in the games to watch and talk to each other so the regular players cant hear them like Roger Wilco or MSN but I also know connectivity hackers do the same thing accept to cause harm.
Barton 3200+ 400MHz
A7N8X Deluxe
Air Cooled 45C
2x512 Corsair DDR 400 PC3200
GeForce FX5900
Two Maxtor 40Gig 8MB cach 7200rpm
SONY RW 52x/24x/52x
SONY DVD 16x/40x