During the installation im getting a message 'cannot install system on this machine' i asume this hapens, because the CD is dedicated for pure HP machine (the CD is marked 'only for new HP machines'). My question is, if i can install a trial version and use the cdkey which is provided with the OEM version?will it work?

No, it probably will not, OEM keys are specific to OEM versions of Windows, so you will likely need to purchase a retail key. -- Mike Burr

Hi, I think the answer is NO. The following post discussed a similar issue, you can refer to: Problem with ACER vista COA OEM keys, says invalid? http://social.microsoft.com/Forums/en/genuinevista/thread/4714bfed-9776-4a7c-814f-ab829790dab3 By the way, if you want to get a definite answer, it is recommend that you contact Microsoft License Center so that a dedicated Support Professional can assist with your request. Best Regards, Vincent Hu