XPS 600 with 4 gB Ram not detected

​ Hey I know this is all over the forums, but my case is alittle different. I have 4GB of PC5300 @ 667 4X1GB chips. The bios detects all 4 of the gigs yet when I run xp mce it only shows 2 gigs. I can live with the3 gig issue everyone is having, but how can i physically see at least 3 gigs. ​

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​ I need the extra gig to continue working on a power point project. So far I get error messages saying theres not enough memory and when i open the task manager sure enough its maxed out at 2 gigs. ​

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​ At this point I'll take any help. I've tried all the things on the ms website, but i feel like im missing something. ​