Ah, here it is. Only 4 years though.
My home computer is nearly always on. Currently, 72 hours since reboot.
However, at work, the three computers that run the radio station automation have been continuously powered on since 1994. Yes, that’s correct. 1994. 75 MHz jobs, on DOS.
I shut down my computer every night, and boot it up every day. My main machine is a laptop. My desktop has been on for about ::thinks:: three weeks now, mostly because I’m too lazy to shut it off.
I would tell you, but I don’t know where to check. 
Christ!
Same for me. I also put the modem on standby when I turn the computer off. I see no reason to leave it running while I sleep or go to work.
At work, they want us to reboot at least every 40 hours, which is no prob for me, since I’ve got a wonky machine that has to be rebooted at least twice a week. Yep, nothing but the best for us gummint employees…
You can’t use the CPU time of the System Idle Process if your machine has more than one physical CPU, or (more likely) hyperthreading turned on. If so, note that the CPU time increases at some multiple of real time (two seconds of CPU time pass every second of real time on a single hyperthreaded processor, for example).
Since almost all reasonably modern P4-based machines have hyperthreading, this likely applies to you.
It’s also worth mentioning that even on a single-nonHT processor, the uptime would be the System Idle Process PLUS all the other processes.
OK, so what is the correct way to see uptime on a Windows XP box?
There isn’t one, directly. A programmer wouldn’t have much trouble writing such a utility, one of the Win32 system calls (GetTickCount()) measures time in units since startup, although it rolls over at 49 days.
A few utilities give you “uptime” as a side effect: “net statistics workstation” at a command prompt will have the time of last boot in it’s info (near the top).
[friedo@groovy ~]$ uptime
19:12:58 up 149 days, 3:00, 7 users, load average: 0.00, 0.00, 0.00
My previous record on that box was over 14 months, but then the PSU shat itself.
Interesting, and it tallies with my expectation that unless you can measure it in years, it’s not noteworthy. I remember when I did my internship at Sun one of the engineers had an old Sparcstation amongst his collection of testing machines which had been running continously for something like 5-6 years. However for home users the hardware and operating system situation changes so rapidly that a computer that old is unlikely to be of any use any more, even if power outages and hardware failures allow it to keep running.
To get into double figures you’d need something that has run since 1995, which would probably mean something like a P100 or equivalent running Win3.1 or Warp or whatever. Not hugely likely in a desktop, but maybe there is an old server out there which has lasted this long. Be cool if someone could find one…
I reboot daily. If I leave my computer on overnight my internet connection dies.
$ uptime
15:57:01 up 131 days, 2:22, 9 users, load average: 0.13, 0.07, 0.01
If you don’t reboot how to you get all your allocated memory back from applications you’ve closed?
$ uptime
15:54:29 up 330 days, 20:03, 6 users, load average: 0.05, 0.24, 0.18
That is just time since the last warm reboot (due to a kernel upgrade). I can’t even say when my last cold start was.
You don’t say what operating system you’re on, but this isn’t a problem for modern ones. Both Mac OS X and Windows 2000/XP release memory correctly on application shutdown: even a crash will release the memory properly. You can watch it happen in top / Task Manager if you need to be convinced.
Even on older Win9x-era OSes, failure to return memory when a process exits would be a bug. It certainly doesn’t happen every time you close an app, or those OSes would be unusable within hours of booting for a heavy user.
Ah hahahahahah.
Sorry. It’s just that this was the funniest thing I read all day. 
Getting memory back. Tee hee hee.
The UnaServer has gone 6 months without a reboot.
But I can beat most of you - at work I had an NT 4.0 machine that went from about April 7th, 1999 to about December 21, 2004 (I say “about” because I’m unsure of the exact day; from my e-mail trail it’s unclear if I did it over a weekend or not those weeks), without any reboots. And then I only rebooted it because I wanted to see if it would do it.