My problem is stated below?

Whenever I am trying to format the hard disk of my toshiba laptop it is giving me the following message. Make sure any hard drives are powered on and properly connected to your computer and that any disk related hardware configuration is correct. This may involve running a manufacturer-supplied diagnostic or setup program.
Setup can’t continue. What would be the problem? May be the disk is sata if so then from where should I download the other softwares for it with the xpsp2 cd.

I have a dell optiplex gx 260 – new hd 500gb, 2gb memory. 2 cd/dvd writers. This was working fine. I reloaded the os and then restored the data 2 months ago. 9 days ago turned on the computer, saw the dell splash screen with options of F2/12 then splash screen went off like normal and all I had was a blinking prompt in the upper left hand corner of the screen. Booted to diagnostics – all passed. Swapped power supplies. same result wouldn’t boot from hd. Reformatted hd, reloaded windows and minimum software – office, anti-virus, adobe stuff, firefox. Added users. Worked great.
Next day wouldn’t boot again. Followed same process of reformatting hd and loading os and sw. This time made ghost image. I have reloaded the ghost image 5 times and the computer runs great for a day. But it will not boot again after a day. I have even swapped hard drives.
Any idea what the problem is?
Running Windows XP SP3

I have a laptop and a desktop PC (vista and XP respectively). In the past 1 – 2 months, they both seem to run significantly slower. In particular, surfing the internet is very slow; loading pages can take minutes or not load at all. Reloading a page sometimes helps. This occurs regardless of the browser used ( I have used IE, firefox and chrome, all with the same result).

I have done the following and nothing has helped:
– run a registry cleaner
– run AVG and Adaware anti-virus and anti-malware programs
– cleaned the hard drives and defrag’d them
– ensured I have more than 500 mb space on the "C" drives (I have plenty of space)
– removed non-essential programs from auto start up
– verified the speed of my internet connection

Any suggestions would be appreciated.

Thanks.

2007-Present
American Pacific College Teacher /Computer Repair and troubleshooting-Prepare student for A+ Certification tests, Installation configuration and troubleshooting techniques of PC Hardware/software such DOS and windows. Take down and inspection of PCs and overview of architecture, installation of Hard drives configuration of CMOS and installation of peripherals. Configured PC for Internet connection set-ups, e-mail. Responsible-Installation and Configuration of Network –Diagnostic and Repair Network Equipment Installation Internet for DSL…
Los Angeles, CA

2007-Present
Teacher /Computer Repair and troubleshooting-Prepare student for A+ Certification tests, Installation configuration and troubleshooting techniques of PC Hardware/software such DOS and windows. Take down and inspection of PCs and overview of architecture, installation of Hard drives configuration of CMOS and installation of peripherals. Configured PC for Internet connection set-ups, e-mail. Responsible-Installation and Configuration of Network –Diagnostic and Repair Network Equipment Installation Internet for DSL…
Los Angeles, CA