DialogBoxes:

DialogBoxParamA
GetDlgItem
GetDlgItemInt
GetDlgItemTextA
GetWindowTextA
GetWindowWord

MessageBoxes:

MessageBeep
MessageBoxA
MessageBoxExA
SendMessageA
SendDlgItemMessageA
 

Registry Access:

RegCreateKeyA
RegDeleteKeyA
RegQueryValueA
RegQueryValueExA
RegCloseKeyA
RegOpenKeyA

Reading/Writing files:

ReadFile
WriteFile
CreateFileA

Reading data from INI file:

GetPrivateProfileStringA
GetPrivateProfileIntA
WritePrivateProfileStringA

Reading data (other) :

LoadStringA
lstrcmpA
MultiByteToWideChar
WideCharToMultiByte
wsprintfA

Time And Date:

GetFileTime
GetLocalTime
GetSystemTime
GetSystemTimeAsFileTime
SetTimer
SystemTimeToFileTime

Creating a NAG-window:

CreateWindowExA
ShowWindow
UpdateWindow

Find messageboxtext :

SendDlgItemMessageA
SendMessageA
SetDlgItemTextA
SetWindowTextA

Basic registration scheme:

GetdlgItemTextA
GetWindowTextA
lstrcmpA
GetPrivateProfileStringA
GetPrivateProfileIntA
RegQueryValueExA
WritePrivateProfileStringA
WritePrivateProfileIntA