Need help with memory upgrade PLEASE

Current specs are below.  I'm using Windows Vista Basic with 32-bit.  Can you help me out with whether I need to replace both 512's with (2) 1GB or replace one 512 with (1) 2GB?  Also, should I get the 5300 DDR2 667 or the 6400 DDR2 800?  Thanks.

 

Quantity            Parts #            Part Description

 

1          YK727            Processor, T2060, 1.6, 1MB Pentium Yonah, D0

1          DF261            Assembly, Adapter, Alternating Current, 65W, Mobile 2007, Hipro World Wide

1          JP969            KIT..., SOFTWARE..., DELL MEDIA DIRECT..., 3, VSTA, DIGITAL VIDEO DISK DRIVE...

1          DF771            CORD..., Power, 125, 1M, C7, 2P Dual, United States

1          NC929            Keyboard, 87, United States ENG, SINGLE POINTING..., D Plus Series

2          Y5522            Dual In-line Memory Module 512MB, 533, 64X64, 8K, 200

1          KD882            ASSEMBLY..., BASE (ASSEMBLY OR GROUP)..., NOTEBOOK..., UNIFIED MEMORY ARCHITECTURE..., 6400

1          DY654            Kit, Software, Works, 8.5, Office TRIAL, English

1          YY186            Kit, Software, Overpack, VHB32 Digital Video Disk Drive English

1          PY470            Hard Drive, 160G, Serial ATA 9.5, 5.4, H080

1          UD264            Battery, Primary, 13.2V, 6C Lithium, Sanyo

1          UJ368            Assembly, DVD+/-RW..., 8X, TOSHIBA SAMSUNG STORAGE TECHNOLOGY..., SULLIVAN/TOBAGO...

1          PC559            Card, Wireless, Minicard, DW1390 Broadcom Corporation

1          CD516            Liquid Crystal Display 15.4WXGA, VIDEO ELEC. STDS. ASSOC...., Length

1          KN358            Assembly, Cable, Coax, Liquid Crystal display, Single, 6400

1          NF882            Bezel, Assembly, Plastic, Liquid Crystal Display, 15.4, 6400

4          2864D            Screw, M3X3, K SCREW HEAD..., MICROSOFT..., BLACK OXIDE...

16        3R690            Screw, 2.5X8, #1, K Screw Head Microsoft Release Candidate Camium Plated Steel.

1          6337P            Label, Service Tag/Express CodeCorona

4          63PDH            Screw, MOSAIC/MIDAS,M2P3,M2P4 & TANG..., 5X5, Phillips Head, THREAD FORMED..., BCS

1            MK442            Heatsink, CPU/MCH, Notebook, 6400