Hi David,
Further to the above suggestions from @abrsvc, @dancomptia and @jayeff, I had a look up online in relation to System Memory for Intel DP35DP. The article is given below.
[link|https://www.intel.com/content/www/us/en/support/articles/000006525/boards-and-kits/desktop-boards.html|System Memory for the Intel® Desktop Board DP35DP]
According to the article, the maximum memory Intel DP35DP Board supports is 8GB (thought this might be helpful with regard to memory upgrade).
All the best!