All of the listed modules are 100% IBM Compatible memory modules or kits that are guaranteed to work and meet the IBM Original Specs from the factory. These are not Factory originals. IBM PART# 73P4971 Compatible 512MB PC2-4200 DDR2 Memory Kit $49.00 IBM PART# 73P4971 Compatible 512MB PC2-4200 DDR2 DIMM $55.00 IBM PART# 73P4983 Compatible 512MB PC2-5300 DDR2 Memory Kit $56.00 IBM PART# 73P4972 Compatible 1GB PC2-4200 DDR2 Memory Kit $98.00 IBM PART# 73P4984 Compatible 1GB PC2-5300 DDR2 Memory Kit $110.00 IBM PART# 73P2867 Compatible 4GB PC2-3200 DDR2 Memory KIT $600.00 IBM PART# 30R5145 Compatible 8GB PC2-3200 DDR2 Memory KIT $1,600.00