48GB RAM, CentoOS only sees 15GB

the BIOS reads all 48GB perfectly, the OS only reports 15GB, I don't know why.. any suggestions?

I know I should be thrilled to have 15GB of RAM but I put 48GB in there for a reason.

EDIT: output of cat /proc/meminfo:

MemTotal: 15455596 kB MemFree: 14923768 kB Buffers: 78988 kB Cached: 136164 kB SwapCached: 0 kB Active: 101916 kB Inactive: 154792 kB Active(anon): 43904 kB Inactive(anon): 1052 kB Active(file): 58012 kB Inactive(file): 153740 kB Unevictable: 12708 kB Mlocked: 12708 kB HighTotal: 14812744 kB HighFree: 14601372 kB LowTotal: 642852 kB LowFree: 322396 kB SwapTotal: 43007992 kB SwapFree: 43007992 kB Dirty: 4 kB Writeback: 0 kB AnonPages: 54376 kB Mapped: 32160 kB Shmem: 1276 kB Slab: 210116 kB SReclaimable: 49976 kB SUnreclaim: 160140 kB KernelStack: 2936 kB PageTables: 3552 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 50735788 kB Committed_AS: 257280 kB VmallocTotal: 122880 kB VmallocUsed: 15924 kB VmallocChunk: 96784 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 6136 kB DirectMap2M: 901120 kB 

uname -a output:

Linux server.local 2.6.32-131.21.1.el6.i686 #1 SMP Tue Nov 22 18:21:07 GMT 2011 i686 i686 i386 GNU/Linux