Is a (1gb 2rx8 pc2-5300-555-12) the same memory as a (ddr2 pc2-5300-667)

The memory is the same speed. The timings may be different because they have not been listed on the second one and '2rx8' is that the number of ranks the stick has, also unkown on the other stick. I can't be sure that they are the same but they seem compatible. What are you trying to do?

I am trying to upgrade my ram from 3gigs to 4gigs. Windows 7 DEP is on.

there are 8 banks on the ddr2 pc2-5300-667

I am using a 32bit system with win7

So you need another 1gb stick? or replace an older stick with another. Please tell me how many slots you have and what is currently in each of them. Also note that with Windows 7 32 bit, it will most likely not recognise more than 3.5gb ram.