I have a question about Dimm memory boards. I bought a computer at garage\nsale. It is an HP Pentium 4 with a 1.5 Ghz processor, Windows XP. When I got\nit home I found that it runs much slower than my Pentium 2 with 500 Mhz\nprocessor and 256 k of memory that I am currently using. In fact, it takes\naround 3 minutes to boot up and when it boots up it takes over one minute\nfor all the icons to appear on the screen. The longer I use the computer the\nslower it gets which makes me suspect insufficient memory. I ran virus and\nspyware/adware checks with recently updated Symantec and Zonealarm and it is\nclean of them.\n\nI opened it up and found one 256k memory board installed that looks like it\nmay not be the original one that came with the computer. I pulled it out and\ninstalled a 512K memory board and the computer refused to boot up with it. I\npulled it out and installed two 128K memory boards and it booted up but\nstill slow. I pulled them out and installed a 256K memory board and it\nbooted up a little faster but still very slow. I noticed that several of the\nspare Dimm memory boards that I have have labels on them that tell the size,\nsuch as 128K, 256K, etc., but some also say "100 Mhz", "150 Mhz", etc.\n\nDoes the 100 and 150 Mhz matter? Is it okay to mix/mismatch the 100 & 150\nMhz memory boards in the computer? Also, some of my Dimm boards say "Dell",\nsome say "HP", and some are off brands. Does that matter? I tried to run the\nXP version of scandisk and it says that it cannot check the disk because the\ndrive or a program has exclusive use of the drive. I wonder if that is due\nto the memory boards. Thanks for helping out on this.