Windows 7 professional on vaio issues

My Z series vaio came with windows 7 professional 64 bits system 4 GB of memory i5 processor but the issues are as follows:-

1. the wireless seem to retain the previous DNS information if you move from one wireless to the other.
2. it freezes every so often especially when using explorer and outlook

i increased the memory form 4GB to 8Gb
should fly but issues all the time, the question is what is the issue

karl