I have a Toshiba laptop. I left it logged onto the internet permanently with little security, and it has crashed. I tried to use the product recovery cd and it didnt work. It kept on saying something like: incorrect hardware. I looked on these forums and someone was having a similar problem, i followed their solution which was to set my boot up in the settings to the cd-rom. However now it only says operating system not found, and i can't get into setup or type anything, if i do, it just repeats the message. Can anyone help?

Welcome to TechSpot
What Windows version are you trying to install?
If your laptop has a floppy-drive, change the BIOS to start from floppy and try the startup-disk from W98, to see if there is anything at all on your harddisk.
You may have a hidden directory on the HD with the install-files.
If the floppy starts (with CD-support), then insert your CD and do the installation that way.

Are you sure you set it to boot from CD-ROM and that the CD-ROM you are booting from is actually bootable? You can't boot from an external CD drive either.