Hi Romeo,
The pack that Trevor is referring to is a Voice and Style Expansion (VSE) pack for the PSR-S950/750 and the A2000. It contains additional voices which use new wave samples contained in the pack as well as 40 styles. The pack loads into the built in flash expansion memory that these keyboards contain. Unless you have one of the above keyboards you will not be able to load the pack and use the voices.
However there is a piece of software which can 'extract' the styles from the pack and produce individual style files. However the styles are in SFF2 (SFF-GE) format, which means that you would have to convert them to SFF (SFF1) to use on a Tyros1, if that is what you still have.
Even after conversion, many of them use some of the new voices from the pack which won't be available to you, so you would need to re-voice them, guessing what the instrument is supposed to be.
If you are still interested here is a link to the Yamaha site from where the pack can be downloaded. Scroll down the page until you find it. There are other free packs too. This is the UK site but if it doesn't work for you, there should be a link from European Yamaha sites ...
Voice & Style Expansion - Special Site - Yamaha - UK and Ireland
The software to extract the styles and to convert them to SFF1 is from Jørgen Sørensen's site...
YAMAHA Keyboard - Home
The programs that you need are 'Style In YEP Files' and 'Style Format 2 Converter'
Regards
Ian