Hi Prayami

1. What link to Windows Vista SP1 download are you referring to?
2. Is it Vista beta RC or RTM
3. If you are already running a vista beta then the next upgrade should not effect your existing software. However remember a beta version is something thats released to find and correct "bugs"
4. Always remember the golden rule about setting "system restore" points before installing new versions of any OS.
5. Most professionals who have tested the different Sp1 betas & RTM version have reported no significant gains in terms of speed. However there does appear to be an improvement in stability and compatibility with existing hardware.

The choice is yours! If in doubt wait another few weeks till the SP1 is available as a Windows Update Download.