alternatehistory.com

Commodore 64
C64 gaming still had a ways to go in terms of entering the mainstream, but the release of Lode Runner for the system helped kickstart the computer's gaming scene. While the ZX Spectrum was dominating Commodore on the European front, Commodore proved strong in North America. Little did they know their British rival had plans for the American front...

Timex Sinclair ZX Spectrum
The partnership between Timex and Sinclair allowed for Sinclair to easily export their products to the other side of the pond. Timex originally had plans to release a modified version of the ZX Spectrum called the TS2068 but Sinclair heavily pushed Timex to just release the Spectrum as-is. Timex Sinclair would end up with a sizable amount of share in the computer market, and in terms of gaming, titles like Manic Miner and Jetpac kicked off its gaming scene.

Compaq 1000/1000X
With the computer business off Atari's back, Compaq entered a conundrum as to how they should continue Atari's line of 8-bit computers. Before selling their computer division, though, Atari did have plans for upgraded versions of the 400 and 800 with less expensive parts. Compaq ended up taking the gamble and went through with making the computers Atari abandoned, only with Compaq's branding instead of Atari's Mt. Fuji. The computers ended up moderate successes by the end of the year,, with computer magazines deeming Compaq a worthy successor to Atari.

Apple Lisa
Apple's 1983 machine wasn't quite as lucky. Upon launch, the Apple Lisa was known more for its poorly designed and overall unreliable floppy disk system then its implementation of a graphical user interface. While Steve Jobs was involved in the product's development, he was kicked out of it early, prompting him to develop a different kind of all-in-one GUI-based computer. The Lisa sold barely enough to keep Apple afloat by the end of the year.

Microsoft announces their GUI
Whereas Apple had been experimenting with GUIs for a few years, Microsoft had been doing so since 1981. In November 1983, however, Microsoft publicly unveiled their work in progress, with the codename changed from "Interface Manager" to "Windows". A full release of the product is to be expected in two years.