What are the disadvantages of getting an OEM of XP?
Is it worth paying the double for the retail version?
OEM http://www.newegg.com/Product/Prod [...] 6832116056
Retail http://www.newegg.com/Product/Prod [...] 6837116193

Also what are the diferences between the basic an profesional versions?

What do you need to instal the OS? a cd/dvd drive? (and oviously the pc)

Sorry for bad english

There is no difference between the Retail and the OEM versions. However, the licenses are different. Never having read the license I can't tell you what the differences are but I have never had a problem Activating Windows with a clean install even after I"ve "had" to replace the mobo and CPU. I've never had to lie to get it Activated

To install XP you need a CD or DVD drive, I believe with Vista you need a DVD drive but not with XP. You'll also need your drives, mobo drivers will come with the mobo. It's best to download the latest drivers and put them on a CD, this saves time upgrading drivers. Their usually titled Intel, nVidia depending on the mobo. It's best to install the chipset drivers first. I think that's what they're called, on the CD that comes with the mobo, during auto installation, it's the one that is usually installed first. Your LAN driver should be next so you can connect to the NET. Probably safest to restart when asked when installing drivers but it's time consuming. From what I understand, if you're using a server you should get Professional otherwise Home edition is fine. I know it's easy to set up a home network with a router with XP.