According to this site:
https://www.lpbatt.com/Compaq-Presario-C555NR-Memory-2GB-kit-(1GBx2)-667-SODIMM-PC2-5300-Ram-For-Laptop-Pno-RZ350UA
It says "Each memory slot can hold DDR2 PC2-5300 with a maximum of 1GB or 2GB or 4GB per slot." (Note: Max memory depends on 64bit / 32bit OS. Also manufacturer says 3Gb max but it actually supports 4Gb. )
So on the official Dell Website It said the max limit is 2GB Ram. Which consists of 2x 1GB DDR2 Ram. Well I just installed Samsung 1x 2GB 2Rx8 PC2-6400S-666-12-E3 DDR2 Ram. That works perfectly. Boots up as a computer should Which makes me assume. If that one slot can hold a 2GB Ram Chip when they specifically said highest can support is a PC2-5300 1GB DDR2 Ram I assumed "okay Im going to install the other 2GB thats exactly like the first one in Slot 1. I did so resulting in the computer booting up but no screen. The Ram is not faulty at all bc I've tried it in different computers. Now on the website above it has me thinking (the way its worded) that I can run the 4GB Ram on this computer since it says 1GB, 2GB, or 4GB per slot.
Finally:
Does this mean all I need to do is install a 64 Bit OS like Windows Vista or 7 Home Premium and then It will read the other 2GB I can insert after install? Or what. Bc Every website has told me something different about this laptop.
Added (1). Edit: Also I dont know if it has an affect on this right now or not but I do not have an OS installed yet on the HardDrive due to having complications with write-errors to the harddrive from the official Install Disc. I've tried Windows XP, Windows Vista, and Ubuntu 32 bits and they all have failed to write.
Read more: Is it possible to exceed the maximum limit of 2048mb (2GB) Ram in the Compaq Presario C555NR?