not enough space temporary files

Hello, I'm trying to install Windows Vista. I currently have 3 harddrives, two of them have 25GB of free space and the third, external one, has 45GB of free space.
When I start the installation I get the following error message: Your computer does not have enough space for temporary files Windows installation needs at least 436 megabytes (MB) of free space on any partition for temporary files. Free some space on any partition. [Error: 0x80004005]
One of the 25GB partitions has been completely formatted to NFTS... Any ideas on what could be wrong??
Thank you very much!