Unable to install Basecamp

Don't feel too bad. I also tried to install it on my old XP3 but could not get it going. Net Framework would not install. I have it on my newer laptop... I could not get ITunes to install on my older laptop only on the newer one. All this tech stuff is unbelievable ..a newer version and all is outdated...can't get newer version of IE 11 to connect to garmin .!! Go figure.. :confused:

.....I'm running on Win XP SP3 and I also uninstalled and installed again Framework 3.5 but can't fix the issue.

I'm no professional with regards to .NET. But I do know that some versions of .NET installations do not cover previous versions.
I don't like .NET either, but in the Windows world, it's a necessary evil. So many developers write dependent code.

I'd try installing the other .NET frameworks. Just because you have 3.5 installed doesn't mean previous versions of .NET are supported.

On this Win-7 (64bit pro) system I have v2 (both 32bit and 64bit), v4 (both 32bit and 64bit) and v.4.51 (which is relatively recent.) Some versions must be installed with Windows update, and others can be installed "stand-alone."
I don't know why I don't have v.3.5 (but I can't install it, I tried.) ~ I suspect that unlike v.2, v.3.5 is replaced by v.4.0.

Note: I'm not certain whether the newest versions of .NET can even be installed in XP.

Don't feel too bad. I also tried to install it on my old XP3 but could not get it going. Net Framework would not install. I have it on my newer laptop... I could not get ITunes to install on my older laptop only on the newer one. All this tech stuff is unbelievable ..a newer version and all is outdated...can't get newer version of IE 11 to connect to garmin .!! Go figure.. :confused:

I think that's because of a security setting in ie11. You might try adding garmin.com as a "trusted site" in IE settings, and disable ssl requirements for trusted sites.
I had the same problem but never bothered to fix it. I just use a different browser. Very seldom do I use IE anyways. ~ Used to love Chrome, but reverted to FF, because I'm concerned with privacy.
(Google appears to be "sniffing" everything these days, and using their browser presumably just makes it easier for them.)

Thanks everybody for your feedback!
In fact the first problem I found it was with NET Framework, so I uninstalled it completely and re-installed the 3.5 version, and tried to install again Basecamp. During the process it automatically updated the NET Framework version it was supposed to need (probably 4.51), but after the same error message was displayed :(
I don't need the latest release at all but I cannot find an older release to try taht would be probably compatible with my XP. Anybody knows where can I find an older Basecamp to try?
Thanks again!
Regards.
Daniel

Added for future reference for others: http://superuser.com/questions/252614/do-i-need-all-microsoft-net-framework-versions

Wish the developers would chime in. They could tell you whether you need .NET 4+ for newer versions of Basecamp. If this is a dependency you're out of luck, as v4.5 (and up) are NOT supported in XP. http://msdn.microsoft.com/en-us/library/8z6watww%28v=vs.110%29.aspx

Update: According to this MS chart, you can install version .NET v.4! http://msdn.microsoft.com/en-us/library/8z6watww%28v=vs.100%29.aspx (I'd give this a try!)
FYI: If this doesn't correct things, you may have to uninstall ALL the versions of .NET. Here's a link with removal/reinstall directions and a tool to fix .NET. (As I recall .NET tends to do some strange things in XP, and was occasionally "broken" during routine Windows XP updates.) http://windowssecrets.com/forums/showthread.php/155714-NET-Updates-fail-XP-Home-SP3

PS: Here's the MS link to a standalone .NET v.4 installer: http://www.microsoft.com/en-us/download/details.aspx?id=24872

BaseCamp 4.2 requires .NET 3.5 and runs on XP. 4.3 will probably require 4.5 and will therefore not run on XP anymore.

(XP is now more than 12 years old, official support from Microsoft will end next April. That means no more security fixes. Updating is highly recommended.)