Actually, the c runtime should always be compatible. Apparently R6034 means the that perl.exe is missing a perl.exe.manifest file, a new feature of XP (starting with msvcr80). So, all he has to do is add a perl.exe.manifest, something like

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
  <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="
+1.0">
      <assemblyIdentity
          processorArchitecture="x86"
          version="5.1.0.0"
          type="win32"
          name="Controls"
      />
      <description>Super wxPerl Application</description>
      <dependency>
          <dependentAssembly>
              <assemblyIdentity
                  type="win32"
                  name="Microsoft.Windows.Common-Controls"        
                  version="6.0.0.0"
                  publicKeyToken="6595b64144ccf1df"
                  language="*"
                  processorArchitecture="x86"
          />
      </dependentAssembly>
      </dependency>
  </assembly>
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I'm actually suprised this is the first time he's encountered such an error message.