Dell is charging consumers up to £60 to install Windows XP on some new PCs and laptops.

According to its UK website, consumers seeking to purchase a Vostro desktop or laptop will have to fork out between £10 and £60 extra to get Windows XP as well as Windows Vista Business or Ultimate on their machine.

Although Dell has stopped selling systems with Windows XP pre-installed in a bid to comply with Microsoft's June 30 cut-off date for selling XP licences, the PC manufacturer is taking advantage of the downgrade rights built into Vista Business and Vista Ultimate.

Downgrading lets Dell install Windows XP Professional on new machines, although Vista is still shipped with the system so that buyers can, if or when they want, 'upgrade' from XP to Vista. Vista Business and Vista Ultimate are the only generally-available editions that allow downgrades, and can be downgraded only to Windows XP Professional. By Microsoft's licensing terms, the less-expensive XP Home cannot be installed as a downgrade.

Dell was the first major computer maker to announce it would downgrade Vista in order to continue installing XP after June 30. A few days later, Dell's global small- and medium-sized business software manager, Jenni Doane, said in a blog that while free downgrades would be offered on Latitude, OptiPlex and Precision systems, there would be a 'small fee' on Vostro systems.

Adding Vista Business to a Vostro 1000 laptop, for example, costs an additional £50 above the price with the default operating system, Vista Home Basic. Selecting the downgrade option - Windows XP preinstalled and Vista Business installation media in the box costs £60, however.

On its consumer PC site, Dell doesn't specify whether it is slapping downgrade fees on three systems that can be configured with XP: the 630 and 720 H2C desktops and the M1730 laptop, all part of Dell's XPS high-end line. Dell has said that it will not offer downgrades for any "currently available Inspiron laptops and desktops". Inspiron is Dell's best-selling consumer brand name.

Although Microsoft will stop providing new XP licences to computer makers after June 30, and stop selling boxed copies of the operating system to retailers on that day as well, it has relaxed its own availability rules twice in the last two months for some hardware categories.

In April, it extended XP's availability until June 2010 for light and inexpensive sub-laptops such as the One Laptop Per Child (OLPC) XO and the Asus Eee PC. Two weeks ago, it did the same thing for a new class of low-cost desktops dubbed 'net-tops'.