Firstly if you haven't already joined the SETI@Home project you can find out more or join by clicking the banner above, or this link.
 Even if you have a really quick system completing just one SETI work unit will probably take over 10 hours of your time. If you have more modest hardware this can take anything from 25 to 60 hours.
But it's not all bad news because there are many simple things you can do to decrease the time your system takes. Whilst these tips a aimed specifically at the Windows client, the general principles apply to all operating systems.
The simple fact is that the more tasks your computer has to carry out the slower it carries them out, ideally the only thing your processor should be working on is the SETI program code, with this in mind below is a list of speed ups for the windows client. If you have any tips you want me to include, maybe for the UNIX client then mail me and I'll add them.

• That pretty display SETI@Home produces, takes quite a lot of processor time to produce, so if you let SETI@Home run for long periods in screensaver mode, turning it off make a big difference. To turn it of
  • First open Control Panel, (Start->Settings->Control Panel)
  • Double click Display and click the Screensaver tab
  • Setihome should already be set as you screensaver, click Settings
  • There will be a check box for 'Go to blank screen' enable it.
  • Type in you desired value in the 'Minutes unit blank' this is the time after the screensaver activates.
    
    
• All those programs in your systray how many of them are actually earning there keep? When was the last time you change you display properties from that graphics cards control program?, I'm sure you'll have one most people do! How many of the others actually provide a useful service, do you really need ICQ when your off-line? These are issues only you can decide, but running SETI@Home with no other programs in the systray and no other unnecessary tasks running can make a significant difference to your systems performance.
  
  
• If you run SETI@Home unattended, setting it to connect automatically will make best use of the time but BE WARNED you must make sure your dialup is set to disconnect after say 5 minutes on inactivity as the SETI@Home client does not disconnect, and if you live in a country with a rip-off Telecoms company, as we do in Britain, it can cost you dearly. Bear in mind also, programs like the ICQ client can hold the connection open. Make sure you system will disconnect before you leave it to its own devices.
  
  
• It's worth doing a scandisk and defrag on your hard disk,(Start->Accessories->system tools); to optimize you systems performance, though it won't make any great difference to SETI@Home. You've now done all you can, the only way to safely achieve greater performance is through a hardware upgrade,(though I'm sure there are a few LINUX users who would advise a software upgrade >:o) ).

24/7 burnout!
You may decide you wish to run your system constantly,24 hours a day, seven days per week, to really churn out those SETI units. I would advise before doing this to insure that your system is up to the task, in particular if the only source of 'forced cooling' is the PSU fan then I would suggest it would be wise to install another cooling fan. Many cases have the facility to clip a second cooling fan into the front,(be sure this is working with the PSU fan not against it); also it is possible to purchase extractors which fit in a free expansion slot.Good quality CPU heatsinks and fans are also desirable, make sure the inside cabling is neat and does not unduly obstruct airflow. But remember if you don't feel confident to mess with your hardware, then don't! More damage can be done by ignorance than heat!