I don't have any experience with buying computers online. Anyway, follow the steps given below to find if an online website is legit and safe to buy any product from them or not.
1.Use Whois lookup tool like WhoisXY.com to check the whois information. Legit companies properly update whois database.
2.Check whether domain owner contact details and E-mail address is currently active or not.
3.Take some reviews about that company using Scamadviser.com, Webutation.net.
I am sure above the steps would be very useful to check any company is legit or scam.I hope it will be very useful to you.