Upx Download here

http://upx.sourceforge.net/#download

UPX is a versatile executable packer with the following features:
excellent compression ratio: typically compresses better than WinZip/zip/gzip, use UPX to decrease the size of your distribution ! very fast decompression: ~10 MB/sec on an ancient Pentium 133, ~200 MB/sec on an Athlon XP 2000+.
no memory overhead for your compressed executables because of in-place decompression. safe: you can list, test and unpack your executables. Also, a checksum of both the compressed and uncompressed file is maintained internally.

Quick tip.. Copy the upx.exe in the program directory, goto
the dos prompt and type upx *.dll

Upx cannot the program exe for this software, though
normally you can.

So to maximize the process or if you want a commercial
alternative to do dll's and exe's use Aspack

Asp Pack

http://www.snapfiles.com/get/aspack.html

ASPack is an advanced Win32 executable file compressor, capable of reducing the file size of 32-bit Windows programs by as much as 70%. (ASPack's compression ratio improves upon the industry-standard zip file format by as much as 10-20%. and it
requires no unzipping!)