NONMEM 7.1.2 run time in Windows 7

Dear experts... We noticed that a NONMEM job (using NONMEM 7.1.2) runs much slower in Windows 7 loaded on a new HP workstation (z600 with >32GB RAM, Intel, 12 core CPU) when compared to running in Redhat Linux RHEL 5 on a 2 year old HP workstation (32 GB RAM, Intel 8 core CPU). It takes longer time to reach complete the first iteration with NONMEM on Windows 7. Can anyone please suggest possible reasons for runs being slow in Windows? Thanks, Santosh