Q. Is it permitted to buy a new laptop needed for work during the three weeks?

A. Shulchan Oruch (O.C.551: 17) rules that it is better to abstain from reciting the blessing of Shechecheyanu during Bein Hametzarim (the three weeks). Mishna Berurah (ibid. 98) in Magen Avrohom name explains, that since these are days of desolation, it is improper to bless in them that particular brocho.

Betzel Hachochmo (4:55) and other Poiskim permit even during the nine days, buying utensils that are needed for business or housework, despite their being expensive, such as a washing machine or an air conditioner (see Nitei Gavriel – Bein Hametzorim 1:30:2)

Since it is uncommon to recite Shechecheyanu for a laptop, Horav Shlomo Miller Shlit’a permits buying it, if needed during the three weeks.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a.