Putting in RAM from An Older Computer

So, I have a Compaq Presario, model S4100NX. Apparently it accepts PC 2100 RAM. I also have a much older computer (I got it around 1999 I believe), and it is an IBM, I am not sure of the model number. Today I opened it up and pulled out the RAM sticks that were in the computer (There were two, unexplainably). I have no idea what MB these two sticks are, nor what kind they are. There are labels on them that say PC100-222-620, MT8LSDT864AG, 9944AAM8B. 020

Are these compatible with my computer? If not, what harm could be done putting them in?

Thanks in advance.

 

Your Compaq uses DDR memory, 240 pin and the IBM uses SDRAM 184 pin so, no you can't use them and may do some damage to your mobo in the process.

 

And even if it would work, the older RAM is waaay slower and probably tiny in size, maybe 32 MB or so.

 

As augiedoggie said, these are not compatible.