Is there any way to keep voice recording of last one hour? When i talk to the people they go back from their words. I wonder if our N900 could keep recording of last one hour and rest deleted(time after one hour) like aeroplane balck box keeps reocrd of last one or some hours.

hasn't the person who is being recorded to be made aware that they are being recorded in the first place to make it legit?
or is to be used as your friend said 10pm and then swears blind that they said 11pm then you could play it back to them, then they may think your a bit paranoid though.

Depends where... in canada only ONE of the parties needs to be aware.

think the same applies in the UK.

looks like no one is serius about this

Have a look at recaller, or chat with its developer...

use recaller and set option to automatic recording and record for as much time as u can without awaring the other person...set source as phone if u wanna record ur voice as well in conversation and system if u wanna record the other person's voice only... enjoy..

I am aware of recaller and there no such option that could help me, it does record voice but does not have option that could keep last one hrs rec.

one thing i wanna ask...y u wanna have recording of 1 hr only...i mean the call can be longer or shorter than it... ??

The law in the UK stands as this:

To record the conversation for your own listening only, then you do not need to notify the other person. If you intend for anyone but yourself to hear the recording, then you need to gain consent from the other party as per the Regulatory Investigave Powers Act:
http://www.legislation.gov.uk/ukpga/2000/23/section/1

Basically, if you are recording stuff to make sure you don't forget details, that's fine. If you are recording stuff to use in court (for example), then you have to notify the other party at the start of the conversation that you are recording it.