Variables in strings (part II)

[parksie]

MessageBox(NULL, buffer,MB_OK | MB_ICONINFORMATION);

I think you missed a parameter there somewhere

MessageBox(NULL, "Hello", buffer, MB_OK | MB_ICONINFORMATION);

Also, it's a better idea to use _snprintf as this prevents you overrunning a buffer:

TCHAR pcBuffer[100];
_sntprintf(pcBuffer, 100, Your computer has been on for %d minutes", szTickCount);

One thing about prefixes -- if you're going to use them, then the official prefix for int is i. sz is for NULL-terminated strings.