Laptop memory... I need help!?

Hi, I am having a problem with my somewhat new Toshiba laptop. When I bought it last year around September, it had 4 GB of memory installed. I have recently had a problem with it, and so I sent it in to Toshiba to get repaired under warranty. After I got it back, I installed VMware virtual machine player with 2 operating systems in it: Windows XP and 2000. I set each operating system to have the least required memory, and it didn't even total 1 GB combined. However, I have noticed that my computer has been very sluggish, so I decided to check the System Information. It said I only had 2 GB!!! What in the world happened to my other 2 gigs? I unscrewed the cover on the bottom of my laptop to check the memory, just in case Toshiba shorted me when they repaired my laptop, but I still had 2 sticks of 2 GB each. Could there be a missing driver somewhere or a problem that could cause just 1 memory stick or port to stop working? What should I do to resolve this? Thanks

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