huge windows\installer folder! is possilble to clean it?

I have a win 2003 server with sql 2005.
I am not able to install vs2005 sp1 becouse there is not room enought on c
disk.
On windows\installer folder there are over 5 GB of data, and many files has
same size (there are 8 files of 466 MB) and same datetime.
Is there any way to remove some of them? Are they all necessary.
I did a disk clean up and I was able to have 1,5 GB of free space, but after
try to install vs sp1 the free space reduce again to 800 MB that is not
enought for the installation.
Thank you for any indication
Alessandro Belli