Windows only 
The other day I was having troubles with one of my machines regarding the .NET framework. As you probably already know many Windows applications require that you have a specific version of the .NET framework installed (1.0, 1.1, 2.0, 3.0, 3.5, etc…) in order for them to function properly. Unfortunately Microsoft doesn’t make it very easy to repair or reinstall the .NET framework should it decide to go haywire on you.
The first thing I tried to do is uninstall .NET through the add/remove interface with the hopes of reinstalling it again once that completed. Those hopes were quickly dashed once the uninstall process failed miserably, and left me with a half-installed product that didn’t work. To make matters worse I couldn’t reinstall the .NET framework since the computer was saying that it was already installed, and repairing it was never offered as an option.
I began searching around the Internet to find out that I was far from the only person finding themselves in this little crisis. While looking for a solution I stumbled upon a handy little tool created by a Microsoft employee that will cleanup any .NET installations you have on your machine. It removes both both files and registry settings that .NET creates when it is installed on a computer, but it is recommended that you try to use the standard add/remove programs interface before resorting to this.
What makes this tool so nice is the fact that you can have it remove one specific version of .NET, or remove all of them at once. Just select the corresponding option from the drop-down menu, and you’ll be on your merry little way.
Not everyone may have the same problem I did, but it’s obvious that issues like this are fairly widespread. Maybe Microsoft will fix this in future releases of .NET, but this is one tool I’ll always keep handy.
Download .NET Framework Cleanup Utility for Windows
How dumb that Microsoft don’t just accumulate all .NET versions in one. Maybe there’s a valid reason for not doing it, but it certainly makes it pretty messy on one’s PC. It should be, you either have .NET installed or you don’t.
I have run into problems with .NET installations on many computers. One of the worst issues seems to be when it’s updated it often seems to corrupt some portion of the code which won’t allow for more updates. I have really come to hate .NET though some of the things it gives you the power to do make a a necessary evil. I have used this tool with great success to clean up and reinstall .NET on computers that would not allow it to update.
.Net Frame appears to install itself incrementally i.e. the Updated versions install over the top of the Other version already present, which calls for you to have to remove the latest version first and step backwards. (Thats been my experience)
The addition of the “Service Packs” to the Frameworks necessitated it so if your experiencing an issue with 2.0 Framework and you have 3.5 installed you can’t just replace the broken version without removing the latest version first.
This is because of the “linking” that the framework creates after install. Now this Framework tool is a “Great Addition”, but normally you had to uninstall in “reverse order” to fix the issue.
Windows7 includes Framework 4.0 and trying to downgrade or install Framework 3.5 won’t work. Tried that one. It’s not necessarily the Framework’s gumming up the reinstall it’s the Service Pack add-ins. You can always pull them the “old school way” though it takes quite a bit of time. I’ll set this one aside into the collection.
What I never understood with .NET Framework is the relationship between new and old versions, does a new version require keeping the previous versions or does it sum them all? Indeed Microsoft lacks providing information on what seems to be considered by them in high consideration, I don’t understand that attitude, I don’t understand the gap between delivering a product meant for all Windows systems and information provided as it seems to skilled techies only.
For instance – this is a question! – should I install .NET Framework 3.5 over previous versions (1 & 2 here), or would I be advised to clean up (remove) previous versions with this “Download .NET Framework Cleanup Utility” first ? At this time I’ve been unable to find the answer on our dear Web!
Transcontinental, I can answer some of your questions from experience. If you download the .NET framework 3.5 and install it you will end up with 2.0, 3.0 and 3.5 whether you have any previous versions or not. I do not believe it needs any version of 1.x to function though. However based on experience most people will want 1.1, 2.0, 3.0 and 3.5 on XP systems in order to have the greatest compatibility with apps that are released. An app created with with 1.x is not compatible with any of the other versions. Also, apps created with 3.0 can be compatible with 2.0 mainly due to the requirement that 2.0 be installed to have 3.0 and also to be backward compatible with windows 2000 systems. However if I understand correctly anything created for 3.5 and above will not be windows 2000 compatible. It very convoluted to try to understand. I wish Microsoft did a better job explaining all of this. I myself had had to just work with it to figure out what works and what does not.
It was only last week that I experienced difficulties with net framework in that a program wouldn’t complete it’s installation.
After a few days of trying various tactics finally went to add-remove and uninstalled two 1.x versions of NF, leaving 2x. The program then installed without difficulty.
Like others, I do not understand why MFST doesn’t fix this so that instead of having several versions, an update will update, not add another version. Apparently the oldest was in use in my computer, not the latest!
@leland, @Miles, thanks for sharing your tips and knowledge, as it appears to be confirmed that our knowledge in the domain of .NET Framework is mainly empirical due to – all together now! – Microsoft’s attitude, or rather lacks!
At this time I discover to few applications requiring .NF ver.greater than 2 to be motived to get another 100MB or whatever of extra code.
I’ve heard techies declare their admiration for .NF, but I admit, as for myself, ignorant, having always considered this “thing” more as a pain in the neck than as the very abstract beauty of its lines!
I’ve often wondered the same thing. Naturally you would think that .NET is something that you just keep upgrading instead of having to install new versions. I guess they are trying to ensure backwards compatibility with programs that use features from older versions of .NET, but I’d think there would be some way to do this without making people install several different versions.
“but it is recommended that you try to use the standard add/remove programs interface before resorting to this”
Why?
The add/remove programs knows exactly where everything is installed on your PC. I believe this app looks for all of the default locations and removes files from there.