If you are a student with a .EDU e-mail, I think you are eligible for an academic discount. Check that out.
The 32 bit version on your old laptop is likely an oem version which can not legitimately be transferred to another pc.
One benefit of buying a new copy of windows 7 on a DVD is that it can be used for recovery.
If you have a need for 2 or more copies of windows 7, you could look into the family upgrade pack which sells for $120http://www.amazon.com/Microsoft-Windows-Premium-Upgrade-Family/dp/B002MV2MG0
It comes with both a 32 and 64 bit dvd.