[Dev-C++] How to link a Library?

Hey folks,

I wann a use a function --lets say "int doIt( void )"-- from a
selfwritten, precompiled library --I called it "preObj.o"--

Should be the same like "printf(..)" from "stdio" (I am not shure if the
std* libs are precompiled, but it would make sense, won't it)

Ok.

1) I wrote my lib, saved it as "preOb.c"
2) compiled it via "gcc -c preObj.c"
3) and recived "preObj.o"

The program which wanna use my "doIt()" out of my lib contains "#include
"preObj.h" " with the header of my function.

I told DevC++ to link my lib after compiling by checking 'Add following
commands when calling compiler' under "Compiler Options" and adding
"-lpreObj.o" into the field.

To give the compiler a chance to find my lib I gave it the path under
"Libraries Directory" wich is now
"DEV-C++\Lib;D:\Gregor\Cpp\API\Petzold\scanner\" (My lib's path is
"D:\Gregor\...\scanner\preObj.o" )

But instead of compiling and linking and giving me a running EXE-File I
get this error message:
<ERRmsg>

Building resource file...
D:\PROGRA~1\DEV-C_~1\BIN\windres --include-dir
D:/PROGRA~1/DEV-C_~1/INCLUDE/ --include-dir
D:/PROGRA~1/DEV-C_~1/INCLUDE/G__~1 --include-dir
D:/PROGRA~1/DEV-C_~1/INCLUDE/ --use-temp-file -I rc -O coff -i
D:/GREGOR/CPP/API/PETZOLD/RSRC.RC -o d:/gregor/cpp/api/petzold/rsrc.o
Compiling files :
D:\PROGRA~1\DEV-C_~1\BIN\g++ "d:/gregor/cpp/api/petzold/gerts.cpp"
"d:/gregor/cpp/api/petzold/picture.cpp"
"d:/gregor/cpp/api/petzold/position.cpp" 
"d:/gregor/cpp/api/petzold/font.cpp"
"d:/gregor/cpp/api/petzold/dibfile.c"
"d:/gregor/cpp/api/petzold/response.cpp"  -c -ggdb -mwindows  -lpreObj.o
-ID:/PROGRA~1/DEV-C_~1/INCLUDE/ -ID:/PROGRA~1/DEV-C_~1/INCLUDE/G__~1
-ID:/PROGRA~1/DEV-C_~1/INCLUDE/ -LD:/PROGRA~1/DEV-C_~1/LIB/
-LD:/GREGOR/CPP/API/PETZOLD/SCANNER/ -BD:/PROGRA~1/DEV-C_~1/BIN/ 

<\ERRmsg>

Can someone read, mean understand what I did wrong?
If so It would be great to tell me :-)

	Gregor