Quote Originally Posted by rward30 View Post
For general purposes, it doesn't. Only time I notice anything on my system is when I'm doing online games, or something along those lines, that is extrememly extensive use of system resources anyway. For most people, with standard day-to-day usage of the system though, no noticeable slow down. Also, if you do something that requires a lot of resources, you can always pause the F@H program (what I do when I start my MMO games) with no problem. Just remember to resume the work afterwards.
Yes could pause it like rward30 mentioned (or stop it if it is one of the cards that has issues with two 3D apps from running at the same time - e.g. refuses to go to full screen on the second app). I can't say why for rward30 it is noticeable, perhaps adjusting some settings (e.g. slide the CPU selection to 3/4s and don't accept large projects) would clear things up or perhaps it is because of the client type used (as using the windows graphic client)?

However using the settings mentioned in the console installation instructions on the second page of this thread (and repeated below), it should have no impact whatsoever. i.e. can't tell if running or not, even using benchmarks.

Setting for minimal impact:
Use console client with service option and the following settings
80% cpu use (or less, especially if using a notebook)
Use idle priority
Don't accept large projects
Don't accept advance projects

With that configuration there would be no impact in just about all cases, even with an old PIII-550 with not much RAM.

Here is an article from Tech Report about this:
"Conclusions
The results of our testing couldn't be clearer, at least for the systems we've tested today. Quite simply, the impact of running Folding@Home in the background is negligible. Even the most discerning users won't notice it."
http://techreport.com/articles.x/4341/1
Note they are using higher settings (e.g. cpu use at 100% instead of my suggested 80%) and on older equipment than many people have.

Give it a try (with either client) and let us know how it goes!