I have a two-year old Systemax Venture VXC2 PC, Intel Core 2 E7500 2.93 GHz, Windows 7 Pro 64 Bit. 
MOTHER board holds two DDR2 cards, with a capability of 4GB.
Presently fitted with one 2GB card and one 1GB card, totaling 3GB.
It is my intention to upgrade to 4GB.
QUESTION: Should I buy one 2GB card and simply swap with the 1GB ----- OR ----- buy a set of two new 2GB cards?

I'm inclined toward the latter.

Art
There is no reason to buy 2.If you can find exactly the same brand with all other criteria exactly as the one remaining 2 gb is. You probably do not even need to buy the same brand as long as all other factors are the same but buying the same brand should eliminate ALL potential issues.truenorth
I haven't looked up the specs on the computer to confirm that it will recognize all the 4gb.Sometimes even with 4 gb only slightly above 3 will be recognized. Don't know if that  is a factor in this case. QUOTE from: truenorth on May 05, 2012, 05:10:14 PM

...Sometimes even with 4 gb only slightly above 3 will be recognized. Don't know if that  is a factor in this case.