Where can I find my serial code..

I got a computer for christmas I got it from a second hand place. Got it home and used it for a couple of weeks, then i clicked update, it updated then when I turned it on again I got a message saying that the windows was not genuine, so I looked for my serial number everywhere but cant find it. Will I have to get a new compueter ?

 

Not a new computer but definitely a new OS. It most likely means someone used a copy (pirated) of windows somewhere along the line...
You can buy a copy of windows (it will come w/serial) new retail only, not used or copied
Or
You can try out a linux distro like Ubuntu or PC Linux OS
You will also be able to retrieve any data you may have had in windows (no programs just data..pic,docs etc)
http://www.ubuntu.com/getubuntu/download

http://www.pclinuxos.com/index.php?option=com_ionfiles&Itemid=28
choose " USA (ibiblio.org)" from the list for an ISO image

 

Magic Jelly Bean will tell you the serial Windows is using.

Your PC case may have a sticker with a serial written on it.

Does the "Not genuine" message give you any tips on how to proceed?

 

Belaric Advisor retrieves the serial for some of the more popular software on your computer, so you could use that if the serial is all you wanted.

The website is:
http://majorgeeks.com/download1385.html

 

I've come across several PC's that have unofficial copies of windows on it. for now you can use the computer but you will not get the needed security updates, and eventually you may start experiencing software failures. If you choose to keep using this software I would only save things to an external or flash drive and be prepared for the system to become more unstable.
When you got the error message they gave you a validation site or a windows site where you can get a legitimate copy of windows. before you order it make sure you get the correct version a windows upgrade may not work. If you decide to go to Vista, check with this site windows/compatibility to make sure you computer is vista compatible .