'Missing Operating system'- Windows Vista

My Vista system is much slower compared to my desktop. It is a new Dell desktop which came with pre-installed Vista in it. When I work on it, it lags a lot. I cannot open any folders nor I can start the web browser. The surfing is also quiet slower. When I run more than two programs at a time, the system crashes and reboots. I started Windows Update and that screwed the system more. I am trying to restore the system through Vista recovery disc, but still it is not working. There was starting screen of recovery then the system restarted suddenly. Now I can see only one message on the screen saying that the operating system is missing.

Did you called Dell Tech Support. They will help you in this case. The recovery disc will help you to restore your OS and make your system a bit more stable. But if that does not work then you can expect a hardware failure n your system. You must contact dell and ask for help. As it is not fair to tamper it with some other tools or software. It might affect your system warranty. I will advice you to contact to dell and ask for help on the problem.

Try to restore your system one more time. It would help you. Did you got the recovery cd or recovery partition. If you got the cd then there are chances that it is not working well. You have to contact dell and ask for one more new disc. They ship that for some minimal fee.