[Solved] Dot Net applications that used to run all crash with the same error Hello, I need some help, I think my Dot Net or some other software it needs is borked. The problem is that .NET 3.5 and under are part of the OS on Windows 7, so I can't just uninstall and reinstall them. I have searched a lot trying to find a way to repair the problem, nothing works. This may suggest it isn't .NET itself, but something else the apps need, that is borked, but I can't identify what it is. Let's start at the beginning: Windows 7 version: 6.1.7601 Service Pack 1 Build 7601 x64 Computer Model: Dell XPS 8300 (PSU upgraded to 750W) Motherboard: Stock Dell RAM: 16GB Hard Drive: 1TB + 1.5TB both Seagate (ST31000528AS, ST31500341AS) Graphics Card: NVidia GTX 470 Firewall: Windows Firewall Antivirus: Avast Free The applications that are giving me problems:Nexus Mod Manager (program to manage mods for games such as Skyrim)FileHippo Update CheckerBox Updater (file sync software used with the Box cloud storage service)IceChat 9 (IRC client)They are all based on .NET (not sure which version) The problem: All the apps crash right when I start them. They crash in the same way: "Application_name_here has stopped working" dialog, and if I click "View problem details" I get the following information: Code:Description: Stopped working Problem signature: Problem Event Name: CLR20r3 Problem Signature 01: nexusclient.exe Problem Signature 02: 0.45.4.0 Problem Signature 03: 51dd1f3b Problem Signature 04: mscorlib Problem Signature 05: 22.214.171.124 Problem Signature 06: 503ef855 Problem Signature 07: 258c Problem Signature 08: 0 Problem Signature 09: System.IO.FileNotFoundException OS Version: 6.1.7601.2.1.0.256.48 Locale ID: 4105This example is from Nexus Mod Manager as you can see, but the other apps give almost identical errors except for the executable - in particular they all mention error CLR20r3, mscorlib and System.IO.FileNotFoundException. So of course I googled with that information. I have tried all suggestions that made sense, as well as other suggestions when googling for "repair .NET" and "corrupted .NET". What I have tried:Malware scans with MalwareBytes AntiMalware and SuperAntiSpywareVirus scan with Avastsfc /scannow does not find any integrity violationsI was able to uninstall and reinstall .NET 4.0 / 4.5 but it changed nothing, so I think the apps I listed use an older .NETI tried both the dotnetfx_cleanup_tool, and the netfx_setupverifier_new (obfuscated links : blogs.msdn.com / b / astebner / archive / 2008 / 08 / 28 / 8904493.aspx and blogs.msdn.com / b / astebner / archive / 2008 / 10 / 13 / 8999004.aspx)dotnetfx_cleanup_tool cannot uninstall .NET 2.0 or 3.5 since they are OS components on Windows 7, so no help there.netfx_setupverifier_new is convinced everything is fine with all versions of .NET installed on my system. (which may or may not be true, the only evidence I have is that 4 apps I know use .NET crash on startup)I tried uninstalling .NET 3.5 through the "Turn Windows features on or off" in the "Programs and Features" control panel, rebooting, and then turning it back on. Sometimes I get an error saying not all components could be uninstalled. Other times it works. But no change.I tried uninstalling and reinstalling Nexus Mod Manager and IceChat at least, thinking they were the ones who were corrupted. Again no change. Googling error code "CLR20r3" gives info about this, that it generally means there's a bug in the application which causes it to throw and unhandled exception. However it's suspicious that all these apps throw a System.IO.FileNotFoundException, and they all mention mscorlib in the message. I tried searching to see if mscorlib.dll was missing on my machine, but no, it's where it's supposed to be. I think the mscorlib in the message just means that the code that threw the exception was a function in mscorlib.dll, which would make sense if the app was trying to open a file. I have another problem with this PC: I am not able to install some Windows updates. When I install them, the PC reboots to apply the updates, then at the "configuring updates" screen before getting to the logon screen it says "failure configuring Windows updates, reverting changes", then it reboots again but Windows fails to boot (shell32.dll and ntoskrnl.exe are missing) so I have to do a system restore to revert back to before trying to install the updates. Again for this I have searched and tried lots of things. I mention this because the problem above with .NET applications started happening after the last time I tried to install updates, which failed again. Before that (and I mean right before, literally 15 minutes before), I had used Nexus Mod Manager and it worked fine. So the problems with .NET may also be related to the failed updates. I may be doomed to reinstall Windows, but I'd prefer to consider it a last resort. If only Windows still had a "repair" option on the Windows install CD/DVD... Any suggestions appreciated. Though, if all you're going to do is google the error code above and point me at the first few results, don't bother Thanks in advance.