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Mailbag: Do I need still need older versions of the .NET Framework on my system after installing .NET Framework 3.5 SP1?

Mailbag: Do I need still need older versions of the .NET Framework on my system after installing .NET Framework 3.5 SP1?

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I recently installed the .NET Framework 3.5 SP1 on my system.  Afterwards, I looked in Add/Remove Programs, and it shows that I have all of the following versions of the .NET Framework installed on my system:

  • Microsoft .NET Framework 1.0
  • Microsoft .NET Framework 1.1
  • Microsoft .NET Framework 2.0 SP2
  • Microsoft .NET Framework 3.0 SP2
  • Microsoft .NET Framework 3.5 SP1

Do I need any of these older versions of the .NET Framework now that I’ve installed the .NET Framework 3.5 SP1, or can I safely uninstall them?


When you install the .NET Framework 3.5 SP1, it will also install the .NET Framework 2.0 SP2 and the .NET Framework 3.0 SP2 behind the scenes.  You cannot use the .NET Framework 3.5 SP1 unless you also have the .NET Framework 2.0 SP2 and 3.0 SP2 installed.  Therefore, you will not be allowed to uninstall the .NET Framework 2.0 SP2 or 3.0 SP2 if you have the .NET Framework 3.5 SP1 installed.  If you try to uninstall those versions of the .NET Framework, their uninstall processes will block and tell you that they are needed by another application on your system.

The .NET Framework 1.0 and .NET Framework 1.1 can be installed side-by-side with the .NET Framework 2.0, 3.0 and 3.5.  Most applications that were created for the .NET Framework 1.0 or 1.1 will automatically use the .NET Framework 2.0 instead if it is installed on the system.  In most cases, that means you do not need to keep the .NET Framework 1.0 or 1.1 installed on your system if you already have the .NET Framework 2.0 installed.

However, there are some applications that are configured to require a specific version of the .NET Framework, even if later versions of the .NET Framework are installed.  If you have any applications like that on your system and try to run them without installing the .NET Framework 1.0 or 1.1, you will get an error message that looks like the following:

MyApplication.exe - .NET Framework Initialization Error
To run this application, you first must install one of the following versions of the .NET Framework:
Contact your application publisher for instructions about obtaining the appropriate version of the .NET Framework.

In the above error message, the version number will be v1.0.3705 if you need to install the .NET Framework 1.0, and it will be v1.1.4322 if you need to install the .NET Framework 1.1.

If you end up seeing any error messages like this, you can re-install the .NET Framework 1.0 or 1.1 in order to resolve the errors.  If you don't end up seeing any error messages like this, then you don't need to worry about re-installing the .NET Framework 1.0 or 1.1.

  • This is very informative THANKS for such clear and helpful answers!

    My only problem now is the Windows Security Update for 3.5 won't install on my Windows 7. I've already got .Net 4.

    Should I be worried? I've tried pretty much everything to sort it out but I'm not getting anywhere.

  • Thank you so much,your knowledge is awesome and extremely helpful. I just wish microsoft was.lol,Thanks again ;)

  • Gee, would I like to kick Bill Gates in the pants. This miserable garbage system he is growing is costing us a fortune. If IBM had just taken up 'Oasis'(theos) when offered we would have super speed now without the $billions spent on massive equipment to overcome Gates.

  • so what i don't understand is: if let's say i don't have any .net framework on my pc if i install version 4 or 3.5 they won't work because i don't have the previous versions?... i really doubt that.

  • Hi Calin - The .NET Framework 4.5 and 4 don't require any other versions of the .NET Framework in order to run correctly.  The .NET Framework 3.5 is essentially just an add-on though, and it requires both the .NET Framework 2.0 and 3.0 in order to run correctly.  The installer for the .NET Framework 3.5 will install all 3 of those versions automatically though, so you don't need to worry about forgetting to install 2.0 or 3.0 in this scenario.

  • Thank you for your help. It was clear and saved me a lot of time.

  • Great Teachers!

    From humble student.

  • Nice primer. Thank you.

  • I've said it before-- I'll say it again.  YOU ARE THE BEST!!  Even if half the time I fail to fully understand your cogent, concise instructions.  I remember one time I even emailed you and you wrote back.  You are a true blessing for so many not so informed...

  • It finally worked.  Running VISTAx32.  Uninstalled the .NET Framework 1 and followed netframe repair tool and ended up following in order the numerous updates...  All in all, up to 22 of 'em. Through .Netframe 4 et seq.  Not sure I need them all, but OS's running great!!

  • Hi MJ - I'm glad to hear that you were able to resolve the .NET Framework issues on your computer, but I'm sorry for the hassles that these issues caused for you in the first place.  Also, thank you for the kind words.

  • so after reading all above are you saying that network 4.5 or 4 needs to be installed and the others dont have to be installed since 4.5 doesnt need them to perform correctly. because i have 1.1 ,2.0,3.0,4 client profile ,and 4 extended do i need all of that installed

  • Hi Neece - You're correct.  The .NET Framework 4.5 doesn't require any other versions of the .NET Framework in order to work correctly.  Not all applications will work correctly if you only have the .NET Framework 4.5 installed though, so it still might be necessary to install some of the other versions of the .NET Framework on your computer depending on what applications you use.  I wrote an updated version of this blog post that includes information about the .NET Framework 4, and it might help for you to take a quick look at that post too.  You can find it at blogs.msdn.com/.../10219046.aspx.

    One other note too - the .NET Framework 4.5 is a full replacement for the .NET Framework 4, so it isn't possible to install both the .NET Framework 4.5 and 4 on the same computer.

  • Thank you very much for the lessons........just one more quickly, how do I uninstall NET 3.0 on my pc ???

  • Hi Kinzo - The answer to that question depends on what version of Windows you have on your computer and what other versions of the .NET Framework you have on your computer.  If you have the .NET Framework 3.5 installed, it requires the .NET Framework 3.0, so you won't be allowed to uninstall 3.0 out from under 3.5.  Some versions of Windows come with the .NET Framework 3.0 (Windows Vista) or 3.5 (Windows 7, Windows 8, Windows 8.1).  In those versions of Windows, you can enable/disable the .NET Framework 3.0 and 3.5 by going to the Windows Features control panel (optionalfeatures.exe) and unchecking the .NET Framework 3.0 or 3.5 item listed in there.

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