There is a lot of information on the internet about power supples that you may want to look at. ** This ** might be a good place to start. Remember the power supply is the heart of your system, without it the whole thing is just a money pit........ ** Here ** is the spec sheet for the 4300. Looking at this I see that you can only get 512MB PC133 on your system. If you have 256 now and it is a single stick you are in luck, you can just buy on more and you are good to go. However if you have two 128 MB sticks to make the 256 then you are going to have to decide on buying one 256 MB stick and have 384MB and have one 128 left over or buy two 256MB sticks for 512MB and have two 128MB left over. With the price of PC133 being so low at this time if you can afford it and are planing on keeping you PC for awhile I would get the two 256MB for 512MB total........