Does anybody know, if is it normal, when I tried upgrade SU8 to SU2014 (latest for my Windows XP), and installation ask me for 2GB(!!!) disk space? Moreover, it ask space on my C: system disk, while I want to install it to my D: disk.
SU8 takes about 200MB on my D: disk.
I gave up the installation, because I have not enough disk space on the system disk, so I do not know, if it really needs such huge space, but it seems to me strange 
That’s strange. I just had a look at the installed program list and SketchUp 2016 takes up 344 mb of space while SketchUp 2017 is actually 625. Where did you download your SketchUp installer from?
SU v2014 needs the Microsoft .NET Framework v4.0 runtime libraries, the SU setup routine launches the according MS setup during the SU installation which requires additional disk space in %TEMP% and %WINDIR% which are typically located at "C:".
I saw message about .NET Framework during installation, I have version 3.5, so this is probably the reason.
The question is, if it really needs 2G (MS pages say 850MB for x86 system) and if it really takes such space, or if the new .NET Framework replace the old one.
the disk space required during and after an installation may differ because of temp files required during the installation only. Anyhow, the MS .NET Framework 4.0 is required by SU v2014 and therefore simply needs to be installed.
You may try to open the EXE of the SketchUp setup routine with a ZIP archiver program (or rename to …EXE.ZIP) and rip the SU core installation file “SketchUp2014.msi” to e.g. the Windows desktop, launch the MSI by “r-click > Run as Admin”.
Don’t see file name extensions as mentioned above? Enable them in the Windows Explorer folder options.