[infuzo]

Я во всём разобрался. Вот, если кому-то будет полезно - заимствуйте.
Чтение ini-файла:

Global  INIReadRes$
Function ReadINI(FileName$, KeyName$)
	ReadINIStream = ReadFile(FileName)
	Repeat
		FindKeyT$ = ReadLine(ReadINIStream)
		a% = 0
		Repeat
			a = a+ 1
		Until Mid(FindKeyT$, a, 1) = "="
		FindKey$ = Left(FindKeyT$, a-1) 
	Until FindKey$ = KeyName$
	INIReadRes = Mid(FindKeyT$, a+1, 10000)
	CloseFile(ReadINIStream)
End Function

Запись в ini-файл:

Dim  FileLine$(100000)
Function WriteINI(FileName$, KeyName$, CheckedValue$)
	ReadStream = ReadFile(FileName)
	a% = 0
	Repeat
		a = a + 1
		FileLine(a) = ReadLine(ReadStream)
	Until Eof(ReadStream)
	CloseFile(ReadStream)

	a = 0
	WriteStream = WriteFile(FileName)
	Repeat
		a = a + 1
		b% = 1
		While Mid(FileLine(a), b, 1) = "="
		b = b + 1
		Wend
		If Left(FileLine(a), b-1) = KeyName Then WriteLine(WriteStream, KeyName + "=" + CheckedValue) 
		
		If Left(FileLine(a), b-1) <> KeyName Then WriteLine(WriteStream, FileLine(a))
		
	Until FileLine(a) = ""
	CloseFile(WriteStream)
	
End Function