help with libraries

ok i use the borland c++ builder 5.0 to write my programs but i have one big problem: when i want to use a lib from the net i always get a linker error msg that the library is invalid ("maybe COFF") now i have this conversion utility from borland but when i use it the lib is much smaller than the original lib can you tell me how to convert the libs correct? big thx for help --=[[TheMatrixXXX]]=--