dell wont read the 2 gbs of memory i just upgraded

ok i have a dell 4550 its been sitting in my closet for a bit so i finally got around to fixxing it just replaced all the calbles (ide,floppy,ect...) and upgraded the memory cuz i jacked the 512 tha was in it and put it in my other system. so it starts upfine and i try to intsall xp again from the dell resoure cd and the setup stops and say not enough memory installed xp needs 64 mbs. i have 2 gb in the thing of pc3200 i dont understand y the sytem olny says i have 32mbs any coments would be great im at a loss