Help with upgrade on my PC

I recently added a 20G hardrive to my PC. AT the same time, added 128mg of ram and put an AMD k62 350mhz processor. Since that time I have been unable to successfully add an operating system. get SUWIN errors at differen points of install. Have tried roming new ram, removing all other cards and flasing the bios. Any clues or is just a bad hard drive.