The sample rates of audio files do not need to be manually adjusted to match the project sample rate.

1. Sample rates in VEGAS and ACID are project-based, not file-based. Files imported into a project are automatically resampled so that the resulting audio objects have the sample sample rate as the project.

The project sample rate is also used for rendering.
When you're working on a project, the audio material in the project is already using the adjusted sample rate for playback.
If you are using a particular sound card, be sure to adjust the project settings to match the card's hardware settings. 

2. SOUND FORGE does not work the same way as VEGAS and ACID. SOUND FORGE always attempts to play files using the current file sample rate and bit depth.