The Apple iPad has had very little competition in the tablet computer market so far, and it may stay that way for quite some time if rival tablet makers can't bring a device to market. The latest tablet candidate to fall was one of the most promising: The HP Slate.

Hewlett-Packard's Slate tablet was unveiled in January at the Consumer Electronics Show, and appeared to be one of the farthest along among upcoming tablet models. Now a source from HP is saying the company is killing the Slate project.

This news comes just a day after word that Microsoft was stopping development of the folding Courier tablet concept that has wowed many in the industry. The Slate was much further along in the design process and expected to hit stores within a few months from now. The only real iPad competitor to make it to market so far has been the Fusion Garage JooJoo, which has only sold a few hundred units at most.

What is happening to the competition?

HP's cancellation of the Slate may have much to do with the Windows 7 operating system it was running. Windows 7 may have been too cumbersome as a touchscreen OS for tablets, and and early report on Slate development indicated that responses to the Slate's interface weren't positive.

It may be that HP has canceled the Slate in response to the company's recent acquisition of smartphone maker Palm. Many other manufacturers have demoed tablets running the Android OS (originally built for smartphones) and the iPad has shown that the iPhone OS is adequate for tablets, too. HP may be planning to use Palm's highly acclaimed WebOS platform in tablets, and The New York Times has also reported HP is working on an Android tablet. Either option would negate the need for Windows 7.

A handful of other manufacturers are planning on creating Windows 7 tablets — Lenovo for example — but many of them are turning to Android or other mobile solutions. The Notion Ink Adam, one of the most anticipated tablets expected to come out this summer, will be running the Android operating system. It may be that Windows 7 will end up being one of the most undesirable options for tablet makers going forward.

And with the iPad being the only major tablet on the market right now, it appears the field is wide open for companies to try just about anything to unseat Apple.