Here is the service manual for your laptop:
http://tim.id.au/laptops/lenovo/thinkpad%20a30%20a30p%20a31%20a31p.pdf
You can plug in a Type II or Type III PC Card in this laptop. (P. 46 in the manual)
Here is a really good PC Card which will provide wifi for your laptop:
https://www.amazon.com/NETGEAR-RangeMax-Wireless-N-Notebook-Adapter/dp/B000FFLYI2/ref=pd_bxgy_147_3?_encoding=UTF8&pd_rd_i=B000FFLYI2&pd_rd_r=3f40b080-8c4b-11e8-a9f0-db3dc51fc8a8&pd_rd_w=RK2Zv&pd_rd_wg=teysh&pf_rd_i=desktop-dp-sims&pf_rd_m=ATVPDKIKX0DER&pf_rd_p=1475879231140687736&pf_rd_r=9HT2Z8CP6MG0TFKWZG91&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=9HT2Z8CP6MG0TFKWZG91
It has Wireless-N and WPA2. It will definitely work with Vista, and probably with Windows 7. Here is the information about this card:
http://www.downloads.netgear.com/files/GDC/WN511B/WN511B_DS_17May06.pdf