i have lost my operating system on my toshiba a40-151 and dvd player is not working.any help greatly appreciated.

Oh dear!

Does your PC support booting from a USB device?
When you boot, press F8. Try either restoring your PC with your system recovery partition (if you have one), or choosing 'Last Known Good Configuration'.
What changes where made to the system before this happened?

the only screen i get is insert system disc press any key to continue but cd/dvd player is not working

This may sound a little weird, but I had a problem with a Toshiba laptop recently, it's DVD player wasn't working either. Do you ever get a message at bootup that mentions the IDE missing or something like that? What happened in my wife's laptop is that the DVD player connection was loose, so I had to open up the laptop and push it back into its slot. After that it worked. As far as the OS being gone... do you think it may be hard drive failure? Is the hard drive making a lot of noise, especially clicking? (or as my wife says, it sounds like squirrels fighting over nuts) I'm looking at your model's support page on Toshiba UK, and it looks like almost the exact model of the Toshiba I just threw away... I had just installed XP Pro again after a format and 2 days later the hard drive failed. So my advice is to push the DVD player real hard to make sure it's slotted into its IDE connection, and if the DVD drive isn't working, try to boot from USB (but I don't think BIOS on computer this old will let you). Hopefully the HDD isn't dead.