I tried to add version control on a machine with a quite dated installation of TortoiseSVN (1.5.5 Build 14361 of Oct 2008), but could not start any of the programs in the TortoiseSVN Programs menu due to the error message:
The procedure entry point ? _Xbad@tr1@std@@YAXW4error_type@regex_constants@12@@Z
could not be located in the dynamic link library MSVCP90.dll
I checked and found a library MSVCP90.dll in \windows\system32 (version 9.0.21022.8).
On a different PC, where I am using TortoiseSVN regularly, I found a DLL with the same name under \Windows\WinSxS\x86_Microsoft.VC90.CRT_1fc8b3b9a1e18e3b_9.0.30729.1_x-ww_6f74963e\, showing version number 9.0.30729.1.
Back on the original PC, the same DLL with the same version is found in the same directory. Surprise.
Well, my conclusion is that different versions of the MS C++ Runtime library install in different places, probably depending on the application installing the libraries.
My problem was solved by copying the most recent version of the 3 DLLs (msvcm90, msvcp90, msvcr90) from the WinSxS subdirectory to \Program Files\TortoiseSVN\bin. Works!