Tight supplies of DRAM and predictions of higher prices mean PCs capable of running Vista may be even more expensive when the operating system is unveiled than if it released today.

Several memory makers and chip industry analysts have recently projected continued price increases for DRAM (Dynamic RAM), particularly the widely-used 512MB DDR2 (Double Data Rate) chips.

Last week, for example, U.S. memory manufacturer Micron said during its quarterly financials Webcast that DRAM demand will jump 50 to 60 percent this year over 2005. Spot prices of 512MB 533MHz DDR2 chips, meanwhile, continue to climb, said research firm Gartner last week. DDR2 memory has posted price gains of as much as 5.9 percent in the past week, with memory across the board showing an upswing of 3.7 percent from the previous week, Gartner said.

If DDR2 prices continue to climb, machines to run Windows Vista, Microsoft's next-generation operating system, may cost more when it debuts in January 2007 for consumers.

The minimum memory configuration for a PC capable of running Vista is 512MB, Microsoft has said on its Web site and in documents distributed to partners, including OEMs.

A full gigabyte of RAM, however, will be required on those systems -- typically the lower-priced models -- which lack a separate graphics card and instead rely on shared system memory to power graphics processing.

One analyst chimed in with a warning.

"I'm a little worried about the amount of RAM that people may have on their current machines," said Michael Cherry of Kirkland, Wash.-based Directions on Microsoft when asked about how likely Windows XP and 2000 users will upgrade to Vista. "It's starting to look like 1GB will be the minimum to run the operating system.

"I've been casually saying to friends to put more RAM in their machines, but a lot of people still think that means 512MB."

It's not unusual, however, for operating system requirements to be pegged low, nor for those requirements to be superseded by real-world circumstances. Windows XP Home, for instance, has a Microsoft-defined requirement of 128MB of memory, but virtually all PCs now sold include double that amount, while a large number pack 1GB.