What's the make and model number of your motherboard? This will help us in properly identifying what type of hard drive and RAM your motherboard supports. The make and model number is usually printed in white on the motherboard (the location varies).
Alternatively, if your computer isn't a custom built machine, then you can provide the make and model of your computer so that we can assist you further.
As for the info provided so far, with regards to your hard drive, you'll want either a PATA (IDE) or SATA drive. Which one will depend on what your motherboard supports. If you can't distinguish between the two, the following image may help: http://gallery.techarena.in/data/513/sata-ide_lg.jpg
. Compare the image with your current hard drive. Also, the label on the hard drive will usually tell you it's type.
As for the RAM, based on your current RAM, you'll want DDR-SDRAM DIMMs with a speed of 400 MHz. It's identified as DDR-400 or PC-3200 DDR-SDRAM (PC-3200 for the peak transfer rate of Megabytes per second it supports). DDR-RAM DIMMs have 184 pins (see: DIMM - Wikipedia, the free encyclopedia
). There are other RAM specifications that should be considered, but we'll need your motherboard information first.