Question : Problem: imb thinkpad......partition signature != 55aa

i recently bought an ibm thinkpad 240x with no operating system of e-bay. the seller said i need an external cd-rom drive(already got one) and then load the operating system(windows 2000 pro)? a few seconds after i turn it on i get this message. partition signature != 55aa.
iam pretty new to this so please could you answer as simply as possible. thanks!!!

Answer : Problem: imb thinkpad......partition signature != 55aa

Here is a list of the OS installation guides for this laptop. The only one that has Win2000 is the upgrade from Win 98.
http://www-307.ibm.com/pc/support/site.wss/product.do?subcategoryind=0&familyind=50261&brandind=10&doccategoryind=0&modelind=0&doctypeind=10&validate=true&partnumberind=0&sitestyle=lenovo&template=%2Fproductpage%2Flandingpages%2FproductPageLandingPage.vm&operatingsystemind=49979&machineind=0
And the only installation to a blank deive is for windows ME. Looks like you will require a floppy drive to do this .