In article , The Real Andy writes
[snip]MS has (well I think) documented a small'ish number of 'breaking changes' between .NET 1.1 and .NET 2.0 which (IIRC) are in relatively unused places.
If those 'breaking changes' are not in the areas a program uses then code compiled for .NET 1.1 runs OK under .NET 2.0 (as all my code does).
And as others have said .NET 1.1 and .NET 2.0 are designed to (and always have for me) be installed side by side, although I'd be interested in how 1.1 installs if 2.0 is already installed...
There could of course be things that the writers of a program have done that force the use of a particular version but that isn't the fault of MS or .NET. It occurs to me that if the program writers haven't written the installation package correctly that might also give grief.
Overall I personally find .NET pretty well designed and very productive to work with (for what it's designed for and coming from an ASM, C and C++ background that is).