Junior Stanislas superbly curled the Hammers in front from 25 yards in the 16th minute, but debutant Callum McNaughton’s dismissal two minutes after half time for a professional foul on Danny Hylton proved the turning point.
Luke Guttridge grabbed the Shots’ equaliser 13 minutes from time, following up after Alex Rodman’s effort was kept out by the legs of keeper Ruud Boffin, and Hylton drove home substitute Jermaine McGlashan’s cross with only a minute remaining.
Swindon stunned their south-west rivals with a 1-0 win at Ashton Gate, Italian striker Raffaele De Vita heading home 19 minutes from time with the aid of poor marking.
Paolo Di Canio’s men were well worth their victory in a tie finally taking place after being postponed following the riots across Britain earlier this month.
Everton came from behind to beat League One Sheffield United 3-1 at Goodison in the second round, with all the goals coming in the first half.
Richard Cresswell put the Blades in front but diverted the ball into his own net moments later after keeper Steve Simonsen had got a palm to a strike by Jack Rodwell.
The Toffees then took control of the game, with finishes from Victor Anichebe (37) and Mikel Arteta (42) seeing them into round three.
Bolton also survived an early setback to beat Macclesfield 2-1.
Emile Sinclair, who grabbed both goals in the Silkmen’s first-round win over Championship Hull, put his side ahead again last night but Tuncay Sanli and Martin Petrov scored in the second half to earn Bolton victory.
Luis Suarez inspired Liverpool to a routine 3-1 win over Exeter. The Uruguay striker scored his side’s first goal and then teed up Maxi Rodriguez and Andy Carroll to put the result beyond doubt.
Daniel Nardiello pulled a goal back for the Devon side with an 80th-minute penalty after being fouled by Martin Skrtel.
Blackburn enjoyed a routine 3-1 win over League One Sheffield Wednesday after a flying start at Ewood Park.
Ruben Rochina scored twice in the first four minutes before David Goodwillie made it 3-0 in the seventh minute.
Ireland striker Clinton Morrison pulled one back early in the second half but Rovers were rarely troubled and Rochina twice went close to his hat-trick.
Middlesbrough were equally comfortable in beating fellow Championship high-fliers Peterborough 2-0.
Barry Robson’s drive and a Seb Hines header put Middlesbrough two-up before half time and that was how it stayed.