If you’ve used a previous version of Parallels, you’ll notice a big improvement in speed right away. In previous tests, Parallels 3.0 ran Windows XP/Vista at roughly the same speed as VMware's competitor, Fusion 2.0. Curiously, Parallels 3.0 ran other operating systems dramatically slower than Fusion. Most surprisingly, Parallels 3.0 ran Windows 2000 sluggishly. Clicking on the Start button would display the Start menu, but only after a noticeable delay. Version 4.0 has sped up considerably.

While testing Windows 2000, menus popped up as quickly as if the programs were running under a dedicated Windows computer. Similarly, Ubuntu 8.04 seemed to run much slower on Parallels 3.0 but now runs quickly under version 4.0. Strangely, it seems that Parallels 3.0 was specifically optimized to run Windows XP/Vista while Fusion ran all OSs equally well. With version 4.0, Parallels seems to have optimized their program for all OSs while consuming 15% to 30% fewer resources at the same time.

While running ordinary Windows applications has always been easy, version 4.0 now adds support for DirectX 9.0, DirectX Pixel Shader 2.0 and OpenGL 2, allowing you to play more sophisticated Windows video games than Solitaire or Minesweeper. Performance of graphics-intensive games obviously can’t match the speeds of a dedicated Windows PC, but video game playing is now fast enough to be acceptable, although hard-core gamers will still prefer a dedicated Windows PC instead.