.NET - Can I remove .NET Framework 1.0 or 1.1 now that I have 2.0 or later on my machine?

Yes, you can! cheeers, it's because of side by side execution manner in earlier versions (1.0, 1.1, 2.0). I keep it, cuz it doesn't occupy too much space.

- But there are some breaking changes in .NET Framework 2.0 if you have an application which wants to run on version 1.0 or 1.1 if you remove those versions.

Breaking Changes in .NET Framework 2.0
http://msdn.microsoft.com/en-us/netframework/aa570326.aspx

- Look at the .NET Framework 3.5 Architecture,:
http://msdn.microsoft.com/en-us/library/bb822049.aspx

"The relationship of the .NET Framework versions 2.0, 3.0, and 3.5 differs from the relationship of versions 1.0, 1.1, and 2.0. The .NET Framework versions 1.0, 1.1, and 2.0 are completely separate from each other, and one version can be present on a computer regardless of whether the other versions are present. When versions 1.0, 1.1, and 2.0 are on the same computer, each version has its own common language runtime, class libraries, compiler, and so forth. Application developers can choose which version to target."

- The .NET Framework 2.0 was a generational release over the .NET Framework 1.0 but .NET Framework 3.0 (and later) adds new technologies (additive release).

How .NET Framework 3.0 Relates to .NET Framework 2.0 and Earlier
http://msdn.microsoft.com/en-us/library/aa480198.aspx#netfx30_topic3

"The .NET Framework 3.0 adds new technologies to the .NET Framework 2.0, which makes the .NET Framework 3.0 a superset of the .NET Framework 2.0. You can think of .NET Framework 3.0 as an "additive" release to the .NET Framework 2.0, as contrasted with a generational release where software is revised across the board. (For example, the .NET Framework 2.0 was a generational release over the .NET Framework 1.0.)

Because .NET Framework 3.0 is an additive release and uses the core run-time components from .NET Framework 2.0, it is completely backward compatible with the earlier version. Your existing .NET Framework 2.0 based-applications will continue to run without any modifications and you can safely continue your investments using the technologies that shipped with .NET Framework 2.0."

The same question in social.msdn: Which version of Framework .net?
http://social.msdn.microsoft.com/Forums/en-US/netfxsetup/thread/0387a1d6-404b-48d4-9d8c-53aefcb75d7b

.NET Framework article in WiKiPedia is also interesting:
http://en.wikipedia.org/wiki/.NET_framework

.NET - Can I remove .NET Framework 1.0 or 1.1 now that I have 2.0 or later on my machine?