Mark Boucher's valiant effort went in vain as Kolkata Knight Riders returned to the winning ways by beating Bangalore Royal Challengers by five runs in a thrilling encounter of the Indian Premier League here tonight.In the rain-truncated match, the Knight Riders posted 129 for seven in their allotted quota of 16 overs. The Royal Challengers' slow scoring rate in the middle overs left a huge task for them at the end as they managed only 124 for four.Boucher (50 not out off 40 balls; 5x4, 1x6) and Cameron White (30 off 16 balls, 3x4, 1x6) stepped on the accelerator with some lusty hittings to make it a humdinger of a contest at the Eden Gardens.But disciplined bowling and superb fielding by the Knight Riders thwarted the visiting team's effort to stay them afloat in the tournament.Having managed only 53 for three in ten overs and with the asking rate steeply climbing to almost 13, the duo of Boucher and White put on an entertaining 45-run stand off just 30 balls.But the Aussie was unlucky to run out at the non-striker's end in the penultimate over and that dealt a severe blow to the Royal Challengers' chances.Knight Riders' skipper Sourav Ganguly played a vital part in his side's third win of the tournament. With his medium-pace bowling, he returned splendid figures of one for seven off three overs that put the home side in the drivers' seat at the middle stage.The Knight Riders now have six points from seven games, while the Royal Challengers have moved further down the path of oblivion as they succumbed to their sixth loss in eight ties, managing only four points so far. Electing to bat after nor-wester-triggered rains delayed the start, the Knight Riders lost wickets at regular intervals while the Challengers fielded brilliantly to effect a couple of run outs.For the visitors, South African pacer Dale Steyn (3 for 27) was the most successful bowler.The Knight Riders' opening blues continued as they lost openers Aakash Chopra (2) and Brad Hodge (10) within the first four overs.Chopra, making his debut in the IPL, was beaten by the pace of an incoming Steyn delivery and was wrapped plumb in front of the wicket while Hodge played an atrocious hook to be caught at long leg off Zaheer Khan.Ganguly's runless streak continued, despite a promising start that included two delectable drives. The Knight Riders’s skipper was run out to a brilliant piece of fielding by Cameron White at short cover after scoring 20.The Knight Riders reached 49 for three at the half-way stage and around 50,000 crowd erupted in wild jubilation as the David Hussey went after Kumble, lofting the veteran leggie over the ropes for two back-to-back sixes But the Australian's 26-run cameo off 12 balls came to an end soon as he turned Kumble to fine leg and went for a second run. Steyn sent down a brilliant throw for Mark Boucher to complete the formalities. The pint-sized Tatenda Taibu (15), making his IPL debut, picked up a couple of boundaries off Vinay Kumar but got out while trying to hook Steyn and managing a top edge to Boucher. After the 13th over, there was a confusion when Rahul Dravid asked Steyn to bowl his fourth over. As per the rule, one bowler could bowl four overs and the umpires thought Vinay Kumar had done it. However, the confusion was sorted out and Steyn was allowed to complete his quota.Wriddhiman Saha (17 not out off 10 balls) and Murali Kartik (17 off 13 balls) provided the late sparks to the hosts' innings with an invaluable 34-run seventh wicket stand before the latter was caught by Praveen Kumar of his own bowling.