low internet speed

is that an approx speed , quoted by the ISP, - or are you actually getting this speed on a different PC
First I would try a different known working PC and connect to the ethernet port on the modem/router and use www.speedtest.net and test the speed
next try the same PC connected on wireless
then try your mothers ACER on cable connection and wireless and see how it compares to the known good PC

its always possible theres a line problem and thats the current speed of the line - if it is found to be low on the other PCs ask the ISP to do a line test