Replaced 2 pc3200 DDr SDRAM memory. Now it just beeps

wrong parts, its not support by chipset
Memory -
One of the following
2-GB DDR Synch Dram PC3200 (400-MHz) Non ECC (2x 1GB)
Memory Speed Supported DDR Synch DRAM PC3200 (400MHz) non-ECC
Product documentation

It should this is what dell has for the pc listed on the website
http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&sku=A0740429

Here is the specs of the memory that you can use for this motherboard.

2 x 184-pin DDR SDRAM
PC3200 (DDR400) DDR SDRAM
Maximum 2GB

You should be able to use just 1 stick of 1GB. your model supports
Each memory slot can hold DDR PC2700,DDR PC3200 with a maximum of 1GB per slot.*

here you go mate:

Memory Memory Type DDR SDRAM Number of Memory Slots 2 x 184 Pin DIMMs Supported RAM speeds 266 MHz Max Supported RAM 2 GB

Your Intel D845GVSR has,

1. Two ram slots.

2.Maximum Amount of ram is 1GB for EACH ram slot.

3.Maximum TOTAL Amount is 2GB, (1GB in each ram slot)

4.Uses DDR Sdram at 400MHz, (PC3200), OR
DDR Sdram at 533MHz, (PC4200)

This is an example of DDR Sdram at 400MHz, (PC3200),

http://www.tigerdirect.com/applications/category/category_slc.asp?CatId=1354&name=PC3200-DDR-Dual-Channel-Memory&Nav=|c:1352|&Sort=0&Recs=10

(Not advertising for this website. There are many places to buy ram memory)
512MB + 512MB = 1024MB, or also stated as 1GB
1024MB = 1GB

Yes, it will work. Remember that all memory will operate at the speed of the slowest memory though so unless you're completely replacing the memory it won't increase the speed of the memory.

MEMORY 2 x 184-pin DDR DIMM socket support up to 2 GB Support DDR400/333/266 DDR SDRAM

Copied above from ECS website so the answer would yes as it supports up to 3.2GB/s transfer rates at DDR400

You simply just push the memory into the DIMM socket on the motherboard. You need to use DDR SDRAM but should check what your I/O bus speed is set at. They make 4 different types of DDR SDRAM. They are DDR-200 (PC1600). DDR-266 (PC2100). DDR-333 (PC2700) and DDR-400 (PC3200). The following links should help you out:
http://www.tech-faq.com/unbuffered-memory.shtml

http://en.wikipedia.org/wiki/DDR_SDRAM

The Shutle MV42N can take SDRam or DDR
Each memory slot can hold DDR PC2700,DDR PC3200,
up to 2 gig total. the pc 2700 is DDR333 and the PC3200 is DDR400. Why Stop at 256?