Android Question The directory name is invalid

I have the same error even on empty project. so it must be something envirmental of this pc. any idea?

just found out that launching "B4A" as administrator the issue disappears.

Where is the project saved?

C:\Users\105028248\Desktop\105028248\Desktop\105028248\D\b4a_projects\Projects\LOPA

It doesn't look like a restricted path. Worth creating a new project in your Documents folder when the IDE is not running as an administrator. See if it works.

It looks that your login is 105028248 and account is standard (user).
This can explain, why works under administrator (another login has own subdirectory in C:\Users and own HKCU in registry).

If you place folder D on desktop, correct way will be C:\Users\105028248\Desktop\D ....
Probably, something wrong in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders.

I would do following
1) Chkdsk C:/f and reboot
2) Create new user in Control Panel.