Windows xp professional CD rom sells for $30 online without a license. Do I need a license for it to run?

yes you will need a valid licence to go with the CD.

Also be aware if you have a valid licence it may not go along with that disc either. If its a Dell CD like most being sold out there then only a Dell issued licence will work.

It's illegal to use these CDs.

They are called OEMs. They sold cheaply by Microsoft on the condition that they are installed on one machine and that when that machine s thrown away so is the copy of XP. but people sometimes try to resell them after tha machine has been thrown away. They aren't legally permitted to sell them and you aren't legally permitted to buy them, not even to replace a disc that you payed for legally but lost.

You need a licence to activate your copy of windows. A windows cd without a licence is useless.

A cd without a license is worthless, because you definitly need a license to run the installation.

Those without a license key are only useful if you already have a license but have lost the installation cd.

The others (with license key) might be genuine - they might not.

Go for a reputable dealer. If you buy from ebay make sure that they are a power seller with a good reputation.

Yes. It's probably pirated and won't work once you try and install it.

you buy the one without license if you already have one (the sticker on the computer) and you just lost the CD.Otherwise you have to get a licensed one

Ah, this is easy! Although you can use the CD Key to install Windows as many times as you want, you can only activate the key once. Without activating the key on the second PC, Windows will stop working after 30 days. Each license is for only 1 computer. Sorry chap...