But even customers who get the go-ahead from their PC makers may still find that there are some hoops to jump through. Dell, which is the worlds largest computer maker, will continue supporting hardware on upgraded workstations as well as certain servers only if customers abide by its Dell Technology Advancement Program, which allows customers to exchange a license for Windows XP Professional 32-bit editions for the equivalent Windows XP Professional x64 Edition. Dell charges $40 to cover shipping and handling of its upgrade. The upgrade applies to systems ordered between June 20, 2004, and June 30 of this year."The warranty is definitely still valid for customers who upgrade through the Dell Technology Advancement program," said Rachael Lyon, a Dell spokesperson.Hewlett-Packard Co. is promoting the Windows XP Professional x64 upgrade on appropriate systems, including its personal workstations and its newest business desktopthe HP dx5150, which can be ordered with Advanced Micro Devices Inc.s Athlon 64 chipusing an online upgrade program thats similar to Dells. "This [HP-sponsored upgrade] by no means voids any of our hardware-based warranties," said Jeff Wood, director of product marketing for personal workstations at HP. "In fact, were actively promoting the upgrades on our systems ... across both our Intel-based [workstation] products and our new AMD Opteron-based xw9300." At WinHEC, Microsofts Bob Muglia offered attendees a look at the benefits of 64-bit computing. Click here to read more. Others are still evaluating their stances on warranty support for PC owners who install 64-bit XP. HPs consumer PC group, for one, was still investigating the upgrade issue on Tuesday, a spokesperson said. Microsofts Windows XP Professional x64 upgrade is available to PC owners who ordered their PCs with 32-bit Windows XP Professional factory-installed, starting on March 31, 2003. It will be available for machines ordered until July 31, Microsoft says on its Web site. Editors Note: This story was updated to include information about HPs update policy. Check out eWEEK.coms for Microsoft and Windows news, views and analysis.