I'm using a file sharing program that works best when I just leave my PC on all the time, meaning days on end, approaching a week now. I even disabled some feature that puts it to "sleep" after some hours of nonuse. Apart from electricity costs, could being on constantly harm the computer itself? I have a Dell Dimension E521 that is 1 1/2 years old.

If at all possible, use hard drive sleep. That's where the failure is going to be. Another failure point is the fan, but shutdown systems are emplyed there.

Your more vunerble to power surges, sags, transients etc as well. This is a good application of a UPS and decent surge supressor like the ISOBAR which comes with an equipment warranty. If this was mission critical, I'd add something else, but the cost would be a little higher than the PC. I've used them on a PC that was up nearly 24/7 and the only failure was a floppy drive (mechanical) without a UPS. The UPS can be integrated, such that the PC shuts down when the outage is extended.

In any event, unplug during major lightning storms.

Your monitor would use the most power, if monitor has a sleep mode that would be beneficial or perhaps in the power options in control panel for monitor - I personally keep PC on all the time and monitor off at night

But as far as performance with PC, it is best to restart system every so often, not turn it off, just restart - this will clear out things left in memory cache and help with system responsiveness when restarted

Another concern may be power surges, outages or lightning

Just need a good surge protector attached in case of such things

I always turn the monitor off when I'm not directly at the PC, and everything is plugged into an APC P6R surge protector. My power settings allow the PC to be put to sleep in any time from 1 minute to 5 hours, or never, as I've recently modified it. Is that an interval after nonuse? When the PC sleeps, it won't be downloading or uploading, right? That would also lose any download priorities I have. That's why I disabled it. The sleep feature is presented as saving power, but if you think it's best for the PC itself, please suggest the interval. Thanks.

You still should be able to set hard drive sleep. This is the most critical. Programs execute in memory. Hard drive space isn't needed except if your using virtual memory.

True sleep, it's for a period of inactivity.

I'm using a file sharing program .

You've gotten good advice so far, but I wanted to focus on this part. Most file sharing programs are used to promote the piracy of copyrighted matierial. If you are doing that and leaving your PC on and connected constantly, I suspect the RIAA will be getting to your soon.

The only problem I see is with a Limitation in Windows. After 45 days (appx, can't remember off the top of my head), one of the log files Windows uses gets too large, and Windows shuts down. I think there is a way around it, try Google.

You still should be able to set hard drive sleep. This is the most critical. Programs execute in memory. Hard drive space isn't needed except if your using virtual memory.

True sleep, it's for a period of inactivity.

Dell's power options recommended plan has two different things. One is "put the computer to sleep." The default is never but I changed it to 2 hours. The other is "turn off hard disk after." I left that one at the default of 20 minutes. Do these sound like good settings, and will they allow downloads and uploads? Thanks again.

The sleep will cut off the download, however I don't think the HDD power down will cut it off because you will still be using the HDD if you are downloading.

In Sleep mode, the power supply to non-essential and non-critical component is withheld, and most system operation is shutdown and stopped. All data in physical memory (RAM module) is still kept in internal memory, and whole system is place in stand-by mode, which can be woke up and used almost immediately. In Sleep mode, the power load reduce considerably, saving a lot of energy. However, the power must not be cut off, and must be continue to supply to the computer.

I personally would have set hard drive off to "Off" and go with the sleep option

Rob. I like your numbers. In the device manager under the Ethernet adapter make sure Wake on LAN is enabled. That should allow incoming connections to wake the computer.