Businesses should bite the bullet and move to Vista, a research analyst has said.

"Vista is an inevitability, for a number of reasons," said Ben Gray, an analyst at Forrester Research. He then ticked off several, including Windows XP's announced retirement and unsubstantiated talk about Vista's successor, Windows 7.

Microsoft was retiring Windows XP, and there was no guarantee the company would deliver a next-generation OS such as Windows 7 on time or with compelling features, making Vista the only option.

"They are sort of in a 'caught between a rock and a hard place' situation," said Gray. Administrators may not want to move to Vista, but neither of the alternatives - the older XP and the not-even-officially-scheduled Windows 7 - is attractive, he said.

It will become more difficult to stick with Windows XP when top-tier computer makers pull it off their operating system lists on 30 June, the date Microsoft has mandated that manufacturers stop offering it on new PCs. The company will also yank XP from retail sales then.

And companies considering skipping Vista altogether by migrating from XP straight to Windows 7, may be punished, Gray added.

"To be blunt, customers know very little about Windows 7," he said, noting that with the exception of a few facts - the Vista successor will come in both consumer and business editions and versions for both 32- and 64-bit machines - "everything else is pure rumour and speculation."

Microsoft's poor track record on making release dates and crafting operating systems without discarding major features should make corporate decision-makers take pause, Gray said. "Ironically, one of Microsoft's biggest weaknesses, the unpredictable release schedule of its desktop operating systems, will likely spur adoption of Windows Vista as a result of this lack of faith in Microsoft delivering Windows 7 on time," he said.

"You can't count on Windows 7 being perfect," Gray said.

The ageing of XP and the uncertainty of Windows 7 mean businesses really have no choice: They have to move to Vista, whether they like it or not, he noted.

"We get this question daily from clients: Should they continue to deploy XP, which they know and love, or skip Vista entirely for Windows 7?" Gray said. "We're not here to sell Windows XP or Windows Vista or Windows 7, but Vista looks like an inevitability."

In a report he authored, Gray damned Vista with some faint praise, saying that for large businesses, there was "no viable alternative." Companies may talk about non-Windows operating systems - Apple's Mac OS X and the open-source Linux in particular - but "they're not looking to swap out thousands of users," Gray said.

"Companies are trying to figure out where these alternatives make the best fit, maybe pilot [Mac OS X or Linux] in small batches, but on the whole, it's almost a check-mark kind of thing."

Businesses should put all that should aside and start their migrations to Vista soon, Gray argued. "There's no question that adoption of Vista has been tempered to date," he said, "but now that [Vista] SP1 is out, that's going to help adoption. It's the official blessing of Vista."