Product review (4 stars): Works on Win 7 64 bit
It works for me on Win 7 64 bit.  Don't install the driver that windows update finds (CP210x_VCP_Win_XP_S2K3_Vista_7), use the software from Extech's website (RHT10_V5.6).  The logger works pretty good. I'm using it with&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/Extech-RHT20-Humidity-And-Temperature-Datalogger/dp/B0029VA4DG/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Extech RHT20 Humidity And Temperature Datalogger</a>&nbsp;to measure the difference in indoor/outdoor temperature prior to installing insulation. The device is a little hard to install a battery in, that could have been designed better. The software saves the data log to a proprietary data file and a csv text file.  The proprietary data file allows you to load previous data sets for graphing. The csv file is suitable for import in a spreadsheet for analysis/graphing.