Ricardo, soon a lasieve5f build will be available for windows.
The instructions for windows users are to set:

Run only the selected applications
lasieved - app for RSALS subproject, uses less than 0.5 GB memory: no
lasievee - work nearly always available, uses up to 0.5 GB memory: no
lasievef - used for huge factorizations, uses up to 1 GB memory: yes
lasieve5f - used for huge factorizations, uses up to 1 GB memory: no

at

http://escatter11.fullerton.edu/nfs/...subset=project

Carlos