can I Use ddr3 ram in Intel DG41CN motherboard

Solution
I'm afraid not.

From your motherboard specification page: DDR2 667/800

You'll need to use DDR2-667 or DDR2-800 on that motherboard. It can support a total of 2 RAM modules up to a total capacity of 8 GB.

Edit: Examples of RAM you could use:

Memory: Crucial 8GB (2 x 4GB) DDR2-800 Memory ($99.99 @ Amazon)
Total: $99.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-10-27 15:04 EDT-0400

Memory: Crucial 8GB (2 x 4GB) Registered DDR2-667 Memory ($67.14 @ Amazon)
Total: $67.14
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-10-27 15:04 EDT-0400

Luminary

Admirable
I'm afraid not.

From your motherboard specification page: DDR2 667/800

You'll need to use DDR2-667 or DDR2-800 on that motherboard. It can support a total of 2 RAM modules up to a total capacity of 8 GB.

Edit: Examples of RAM you could use:

Memory: Crucial 8GB (2 x 4GB) DDR2-800 Memory ($99.99 @ Amazon)
Total: $99.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-10-27 15:04 EDT-0400

Memory: Crucial 8GB (2 x 4GB) Registered DDR2-667 Memory ($67.14 @ Amazon)
Total: $67.14
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-10-27 15:04 EDT-0400
 
Solution


Both of them are actually registered ECC modules which are not supported by the G41 chipset:
http://ark.intel.com/products/43798/Intel-Desktop-Board-DG41CN

Best bet for a big set of memory would be grabbing $40-60, going to ebay, and working of auctions of 2x 2 GB DDR2. (2x 2 GB DDR2-800 CL5 will be around that price. DDR2-800 CL6 and DDR2-667 will be cheaper.)
There are actually 4 GB sticks of DDR2 out there, but for complicatedtechnical reasons they don't work on Intel's LGA775 platform. Thats probably the reason why they sell for comparable less than those who do.