Microsoft yanked its $150 Windows 7 Family Pack from the U.S. market last week, saying that the limited time offer had expired.

The page dedicated to the Family Pack now reads: "Thank you for your interest in Windows 7. The Windows 7 Family Pack offer has ended."

Some sellers have taken advantage of Family Pack's disappearance to jack up prices of their remaining copies of the three-PC upgrade by as much as 90%.

The special offer, which debuted shortly before the Oct. 22 retail launch of Windows 7, let buyers upgrade as many as three PCs from Windows XP or Vista to Windows 7 Home Premium. The $149.99 price of the Family Pack represented a savings of $210 over three separate copies of Windows 7 Home Premium Upgrade, which lists for $119.99.

When it announced Family Pack, Microsoft said that the deal would run only while supplies lasted, but declined to specify how many copies it would push into the market or when it would end.

Family Pack wasn't the only discount that Microsoft has offered for a short time. Last summer, it pre-sold Windows 7 Home Premium Upgrade at $49.99 for just two weeks in the U.S.

Although blogger Paul Thurrott first noted the demise of Family Pack last Friday, searches of search engine caches showed that Microsoft pulled the edition as early as Dec. 1, while users reported online that they had had trouble finding the discounted upgrade the week before.

"As of 11-26-09, the Microsoft Store does not offer the Family Pack," said a user identified as "Jen" in messages on About.com. "Their website doesn't have it and I also called and spoke with a rep who confirmed this."

On Dec. 1, someone tagged as "Mark A" echoed Jen's comment. "Yesterday [Microsoft's site] linked me stores around my area that were suppose to sale [sic] it. However, several trips to local outlets was futile. I then called the Microsoft Store and they claimed they had been out of stock for past 2 weeks and can't sale [sic] it."

The sudden disappearance of Family Pack raised hackles. "[I] am frustrated as I had planned on picking up the Family Pack in December. As others have pointed out, there was no warning that the deal was about to expire," said "TonyB" on the same Answer.com thread.

Several sellers affiliated with Amazon.com still listed Family Pack as of Sunday, but had marked up the price between 70% and 90%, to between $255 and $285.

Nearly 60 sellers were also offering Family Pack on eBay Sunday, with Buy It Now prices as low as $225 and as high as $255. Other sellers were taking bids on the software.

Minus the Family Pack, consumers wanting to upgrade multiple Windows XP or Vista PCs to Windows 7 must purchase individual licenses. Sunday, Amazon priced an upgrade to Home Premium at $109.49, a 9% mark-down. Wal-Mart's Web site has the same software for $109.82, while Newegg.com sells it for $109.99. At Amazon's price, it would cost $328.47 to upgrade three PCs, or more than double the price of the now-discontinued Family Pack.

Several prominent bloggers have blasted Microsoft for pulling Family Pack. ZDNet's Ed Bott, for example, called it a "dumb move" in a Friday tweet and "stupid and short-sighted" in a later entry on his Windows Expertise blog. BetaNews' Joe Wilcox, meanwhile, said, "I've got a new spelling for 'Scrooge.' M-i-c-r-o-s-o-f-t," in a Saturday post.

Both Thurrott and Wilcox compared Microsoft's limited-time offer to Apple's permanent discount for its Mac OS X operating system. Apple sells a Snow Leopard upgrade for $29, and a five-license Family Pack for $49, a $96 savings over five separate upgrades.