Server Application Unavailable

I've been working on my project from my development box for months and this morning when I came in I'm getting the 'Server Application Unavailable' error when trying to view the site. The ASP.NET worker process is using the IUSR_machinename account so there should be no security issues. I tried disabling my virus software and made sure that Index Services were stopped with no luck. Any other suggestions? Oh, I did install the Microsoft Security patches that were put out yesterday.It seems that the server on your development box is shutdown, i.e. disabled. You can go through Administrative Tasks and manually start or at the command prompt, type: net start aspnet_state.

Hope this guides you in the right direction.
This did not resolve the problem. I've given the account that the worker process is using admin privs just to make sure its not a security issue. Any other suggestions?
I don't think it is a security issue. Something got turned off. Check your processes to make sure everything is turend on.
I had a similar problem yesterday when I installed the .NET framework SP2. I tried a bunch of different things and eventually got it to work again, and here are the steps that (I think) solved the problem:

The assumptions:
- I'm not sure if I'm using the latest and greatest version of ASP.NET. I believe the version I am using is 1.0.3705.288.
- I'm running IIS 5.1 on WinXP Pro SP1

The steps:
- Open %systemroot%\Microsoft.NET\Framework\v1.0.3705\config\machine.config in the text editor of your choice.
- find the attribute userName="machine" in the <processModel> tag.
- change that attribute to userName="SYSTEM". Save.
- Restart IIS by running iisreset.exe from the command prompt.

Notes:
- Changing the username to SYSTEM is a security downgrade, so maybe if it's a production server you'll need to figure out why "machine" wasn't working.
- in the Framwork\ directory there will also be a never version (v1.1.4322 for me). I'm pretty sure it was changing the earlier version that finally did the trick for me, but if that doesn't work you might want to try changing the machine.config in the newer version as well.

Hope that helps!
I am having the same problem. It seems to have started after installing visual studio.net.
What does userName="machine" or userName="SYSTEM" do?
You changed it can you tell me why you even tried that.
I had trouble finding iis to set a virtual directory and then when I set virtual directory my asp page work.
That same day I installed visual studio.net and the next day and I got this error ( Server Application Unavailable).
Checked eventlog last day before the day with error was last week (week earlier) and next entry was 2 hours after finding error.
The asp.net quickstarts won't even work.
I am only one who has used this computer.

 Windows xp professional
512MB RAM
2.8GHz

Help, deadline coming.

Tim.
I'm hardly an ASP.NET expert (I'm a PHP whiz writing my first ASP.NET app), but here's how I arrived at my solution. A lot of this was/is guesswork, so caveat emptor:

ASP.NET was working fine for me until I installed .NET SP2 (which may ship with the newer Visual Studio.NET?), and it was pretty obvious to me that SP2 broke my ASP.NET. I checked my IIS logs (in %systemroot%\system32\Logfiles\W3SVC1 if you're curious where they are) and saw that my requests were generating 500 errors. Not very informative.

So I starting googling to find out what SP2 changed. Turns out that one of the major parts of SP2 was locking down security. Some post on google groups made me take a look at the machine.config file, and while reading the documentation I came accross this:

userName="[user]" - Windows user to run the process as.
Special users: "SYSTEM": run as localsystem (high privilege admin) account.
"machine": run as low privilege user account named "ASPNET".
Other users: If domain is not specified, current machine name is assumed to be the domain name.

I scrolled down, and sure enough, my userName="machine". Perhaps this was one of the security changes that had been made by SP2? Figured it was worth a try, and low and behold changing the userName to "SYSTEM" (and restarting IIS) made the error go away. The better thing to do would have been to check out the ASPNET account and see what permission it was missing (and it's entirely possible that the problem is elsewhere but running with high privaledge hides it somehow), but I was being lazy and it's a dev box that's not exposed to the Internet.

Not sure if that helps you any, but that's "why [I] even tried that."
Good information to know in case I install SP2. I haven't heard of this problem and Microsoft should have notified users of the change when installing SP2.
I am the one that had the server application unavailable error after installing visual studio.net.
I solved my problem by un-installing the .net frameworkand then going to Windows update where it informed me to install the update for Windows xp professional. Now I think I install the sdk.
Thanks spiralOut for your tip, and you solved my problem.

I don't know if i'm right but this is very strange. I had in this computer both Wserver 2003 with full updates (ASP 1.0 SP2, ASP 1.1) and WinXP PRo equal, in both my applications and webservices runned OK. Stange is that when I reinstall my winXP I had this problem even without the sp2, I tried to install it next, and then I repaired my FrameWork to the original from VS.NET 2002. It seems to me that this isn't a simple error... For years I thought that if microsoft had coded hiden games in Office, then how can I be sure that they don't know when I'm going to the Bathroom???

Sorry for my english, I'm portuguese.
Please follow thefollowing thread for details on description of the problem and the way to fix it.

Hope that helps
Kashif