Trotters boss Gary Megson was pleased to bank the three points, which significantly eased their own relegation worries.
He said: "I'm certainly delighted with the result but we can play a lot better than that. We scored at the right time for the second. When we were playing 4-5-1 in the first half we were under pressure but we switched to a 4-4-2 and the game changed.
"We scored and we were quite happy until Reading put us under pressure in the second half and we went back to 4-5-1. There was a lot of hooting about the second goal but it was a good finish from Heidar."
The home fans had been convinced Helguson was off-side but replays showed otherwise. Megson added: "If it was a good decision then it was a good decision."
It was Reading's sixth straight league loss and they were saved from dropping into the relegation places only by Derby's late equaliser at Birmingham, who are now third from bottom themselves.
Royals boss Steve Coppell added: "We had good spells and bad spells last year but our good spells carried us through. This year we haven't had a good spell of any significance. We have got to score more goals and have more clean sheets.
"If we don't have clean sheets then we don't deserve to stay up."