My friend wants to add some memory to his computer. He has an HP computer, with 128 mb of ram, PC133 I believe. So my quesion is, do celerons have ram added in pairs? I know Pentiums ~¹¾ this, but do celerons need this as well?

It has nothing to do with the cpu but with the mainboard and type of ram you use! The board doesn't care if you fit a celeron or pentium to it as long as they use the same socket! PC133 Ram should be PC133 SD Ram and that should work with single sticks. The old pentiums used edo ram instead and that had to come in pairs on pentium boards. If you want to be sure recheck in the manual and look also about maximal size and combinations of Ram (you may find this also in the description of the board in the manufacturers site! And before you buy check if there is still a slot for the additional ram because if the board has only 2 slots with two 64 MB sticks in it you have to remove 64 MB. If you have to remove a stick it makes sence to buy only one big stick so you can keep the other 64 MB in addition (but make sure the size of the big stick will work on that board!). If you're not sure post your board name and version/revision here and I take a look for you tomorrow (have to leave in a few minutes)!

I think he can just slap a stick of 128mb pc133 in there. Hopefully that will work. Thanks for the help. I'll try to post what he has tomorrow morning, thanks again.