"Remind me I have another question for you," says the caller, as she puts the phone aside to re-start her PC. Having got through to the Windows 95 helpline, she wants her money's worth from Rob Beddard, a secondary response group engineer. After 32 minutes of Mr Beddard's advice, one of three problems has been solved, another has been partially solved and he has promised to look into the third. She is clearly pleased: "Oh, I'm so excited. I love it when things work!"

Mr Beddard is one of around 40 staff at Microsoft's Product Support Services (PSS) site in the UK dedicated to dealing with Windows 95 calls. There are an additional 300 at the five support partners - Digital, ICL Sorbus, Unisys, Stream International and PSC - taking the bulk of the calls, and a further 60 at the PSS centre working on the Office 95 applications suite who can be drafted in to help.

Microsoft will spend more than pounds 12m in the UK over the next year providing support for Windows 95 and Office 95. The number of helpline staff was quadrupled to cope with calls, and there are contingency plans to increase the support by a further 25 per cent if needed. But there are no signs of the PSS team reaching capacity yet. Microsoft has exceeded its targets, putting 90 per cent of callers through to an engineer in less than 60 seconds. The contrast with the US is marked. There, the lines were jammed on the first day Windows 95 went on sale and some callers were kept on hold for up to an hour before reaching the engineer. The managing editor of the New York Post wrote an open letter to Bill Gates complaining that the lines were continually engaged and that the "giant public relations machine" had gone into hiding.

Tony Ettlinger, PSS support manager at Microsoft, says nobody is quite sure why there were so many problems in America. The only explanation the company can find is that the engineers were kept on the line for so long. "They planned really well in the US, but the customers are taking twice as long as expected and about three times as long as the UK," he explains.

In the UK, support lines have been dealing with almost 6,000 calls per day since the launch of Windows 95 - double the typical pre-launch rate. Mr Ettlinger says he has the capacity to deal easily with more than 8,000 a day. Despite higher than expected sales, the lines are not as busy as Microsoft expected. "We're taking fewer calls than we should be for the numbers shipped," he says.

Like all the major software companies, Microsoft has had to increase its support staff number repeatedly in the past few years. In 1990, there were just 40 staff. Now there are 300, making up more than half of the total UK staff. This is partly because more home users and first-time computer users are calling, and partly because the software is so powerful and therefore potentially difficult. "We are called by people who haven't had enough training, trying to do complex things," says Mr Ettlinger.

On the floor below the support engineers, a team of call screeners is busy weeding out the callers not entitled to free support. If they do not effectively screen out those who have illegally copied their software or who should be going through their company support departments, Mr Ettlinger says, the price of their software would have to go up.

Dave Mangar, a call screener, has been given a Windows 95 customer number that doesn't match up. "That's the beta version," he says. Betas are no longer supported. The customer begins searching busily for the right licence agreement. "He's running around like a mad thing!" Mr Mangar says. After two tries, the customer eventually finds the right number and is put through to the engineers. "You have to be quite firm with them sometimes."

The barrage of negative stories about Windows 95 has damaged morale at the PSS centre. In turn, it has made those calling in to the lines suspicious that they won't get through or won't be given an answer to their problem. Often, by the time they call the helpline, they are feeling desperate.

Back on the support lines, Rob Beddard is picking up a call from a user who is having problems receiving faxes via an internal modem. The voice is quavering a little; the caller sounds upset: "I managed to send a fax, but when they sent one back, the phone just rang and rang." Mr Beddard calmly takes him through the set-up procedures until he's found where the fax is set to "don't answer". The caller sounds noticeably happier when he thanks Mr Beddard and hangs up. "You've got to spend time listening to them," says Mr Beddard. "You have to get them on your side."