"When a vulnerable child is in distress, the call an adult makes to the NSPCC Helpline could be a significant point in the child's life," said Tim Hunter, deputy director of fundraising at the NSPCC.
"Tragically we can not deal with every call because of a lack of funds. Even more unfortunately, a child may gain the courage to call ChildLine only to not be able to get through."
The Child Protection Helpline gets around 95,000 calls a year. In 2007 the organisation's free ChildLine service received 2.5 million calls, 900,000 of which went unanswered.
The NSPCC aims to answer an extra 500,000 calls to ChildLine every year, and 18,000 more calls to the Helpline by 2011, as well as expanding its online service.
Matthew Bishop, business marketing officer at Microsoft UK, said: "We want to do everything we can to help the NSPCC reach its target, so if you are already thinking of upgrading your software in the run up to Christmas then this is a great way to do it."
ChildLine said that it is increasing its call centres to 15 next year to cope with the demand, and will need to increase its volunteer counselling force from 1,200 to nearly 1,800 to try and answer every call.
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