Dell Dimesion 2400 Problems

I’ve been working on a Dell that had a problem with spyware. After several attempt at using anti-spyware software (Microsoft, Ad-Aware, CA) I finally convinced the owner that the best solution is a clean install. I performed the clean install, set up the OS, reinstalled the drivers, and reset the ISP specs. Webpages take a long time to load, downloads are non-existent, and now the computer does not boot without going to the option for selecting the OS first.

I have suggested replacing the hard drive but I am not sure if this is the best solution. Any suggestions will be greatly appreciated.