Newer versions of Powder Toy require the Microsoft Visual C++ 2010 Runtime, available on the powder site
http://powder.hardwired.org.uk/vcredist_x86.exe (32bit)
http://powder.hardwired.org.uk/vcredist_x64.exe (64bit)
 or from Microsoft at
http://www.microsoft.com/downloads/details.aspx?FamilyID=bd512d9e-43c8-4655-81bf-9350143d5867&displaylang=en (64bit)
http://www.microsoft.com/downloads/details.aspx?FamilyID=a7b7a05e-6de6-4d3a-a423-37bf0912db84&displaylang=en (32bit)