Originally Posted by cosmos
I already own a copy of Windows XP Pro and have two computers already loaded with the same copy. Can I install the same copy on a third computer? I am trying to save $150 dollars. I plan on buying a 8790 without an operating system.
Legally, no. You may want to read here
"How many installations can be made with one product license? Has this changed with the introduction of Product Activation?
The underlying principles of Microsoft's software licenses have not changed. Microsoft's End User License Agreements (EULAs) have always stipulated the number of PCs that software can be installed on. Product Activation does not change that. Office XP or Office 2003 may be installed on one PC. The primary user of Office may also install one copy on a laptop computer for their exclusive use. To install Office XP or Office 2003 on more than these two devices, another license of the product must be acquired. Licenses for Office XP or Office 2003 acquired preinstalled on a new PC are single-PC licenses that cannot be transferred or installed a second time on another PC or laptop computer. Windows XP may be installed on one PC. There are no secondary use rights (e.g. no "laptop clause") in the Windows XP EULA. The aforementioned licensing terms have not been changed due to Product Activation. Some special licensing programs (such as the Microsoft Developer Network) provide additional licensing terms. Please check your specific license agreement or EULA for specifics. Re-installation and re-activation on the same PC can be done an unlimited number of times. Pricing and licensing details are available for Windows XP and Office 2003."
"Does Microsoft Product Activation allow customers to install products on a laptop as well as on a PC?
Consumers should refer to the terms of the product's End User License Agreement. In some cases, the Microsoft EULA allows customers who are the primary user of Microsoft applications such as Office and Word to install one additional copy on their laptop computer for their exclusive use. This does not apply to product licenses acquired with the purchase of a PC. These OEM licenses are single-use licenses that cannot be transferred to another PC. Windows XP can also only be installed on a single computer. Installation and subsequent activation on a different computer requires a new license."
"What happens when you try to install and activate on more PCs then the end user license agreement (EULA) allows?
Per the EULA, installing on more PCs then the EULA allows would be in violation of the EULA. Technically, product activation does not limit the number of PCs the software can be installed on. It would be possible technically to install the software on, for example, 100 PCs. Activation would fail though on 99 (98 for Office XP or Office 2003) of those 100 PCs thereby limiting the usefulness of the illegal installation. Outside of an activation attempt, Microsoft does not know how many PCs Windows XP, Office XP family product, or Office 2003 System product have been installed on."