Lenovo G450 Constellation Edition memory card model is 2GB. 2Rx8。 Pc3-8500s-7-10-f0.1066 add a memory card, ask for help.

It is best to add a memory stick with the same brand, frequency and size as the old memory, which has the best compatibility and stability. Assuming that both of your memories are good, from what you said, the frequency of your 2G memory is 1066, and the frequency of your new 4G memory is invisible. If it is 1333 or 1600, there is a frequency reduction problem. But also depends on whether the motherboard supports it or not.

If possible, I suggest you plug that 4G into another computer. If you work on another computer, it may be that the two memories are incompatible or the motherboard supports it. Eliminate one by one.