Trouble getting 2.5 working

I'm not really very computer sophisticated but I do use Blender a lot. I've been trying to get a 2.5 Blender to try it out. I've DL'ed the one from Blender Foundation and this one, 2.5 Trunk, from GraphAll.org. I keep getting this same error message and Blender shuts down. Microsoft Visual C++ Runtime Library Runtime Error! Program: C:\:Program Files\2.5 Trunk\blender.exe This application has requested Runtime to terminate it in an unusual way. Please contact the aplication's support team for more information. Can someone tell me what I'm doing wrong or what I can do to get past this? I don't have a clue.