when I turn on my Dell laptop, it says that it has no bootable device. I pressed F2 and in the device it said primary device-none.What shall I do? Which CD shall I put in the computer. I have the CD for booting and I have the CD for the operating System.

Hi,
The CD for booting will return your laptop to the state it was when first delivered. The OS Cd will wipe everything from your machine and just install windows.
Copied from the DELL site.
"You can restore your operating system in the following ways:
• System Restore returns your computer to an earlier operating state without
affecting data files. Use System Restore as the first solution for restoring
your operating system and preserving data files.
• Dell PC Restore by Symantec (available in Windows XP) and Dell Factory
Image Restore (available in Windows Vista) returns your hard drive to the
operating state it was in when you purchased the computer. Both
permanently delete all data on the hard drive and remove any programs
installed after you received the computer. Use Dell PC Restore or Dell
Factory Image Restore only if System Restore did not resolve your
operating system problem.
• If you received an Operating System disc with your computer, you can use
it to restore your operating system. However, using the Operating System
disc also deletes all data on the hard drive. Use the disc only if System
Restore did not resolve your operating system problem.
Using Microsoft® Windows® System Restore
The Windows operating systems provide a System Restore option which
allows you to return your computer to an earlier operating state (without
affecting data files) if changes to the hardware, software, or other system
settings have left the computer in an undesirable operating state. Any
changes that System Restore makes to your computer are completely
reversible."
For more information go to..............
http://support.dell.com/
Enter you machines model etc and search for what you need.