Intermittent slow start up.

My laptop is an Acer 5738Z with Windows 7 Home premium and NIS 2010.It is about 6 months old and I have had no problems until recently.It is an intermittent problem.My welcome screen normally appears in 30 seconds and the wallpaper around 40 seconds.Every now and again,this takes around 70 seconds and 90 seconds.As I said,it is an intermittent problem and can be o.k. for about 10 boot ups then I get the slower times for a few boot ups.I have not installed any new programs that could have caused this.Any ideas what is happening?

Go to start > and in search box type msconfig and then <enter>. Click the startup tab. See if there is anything out of the ordinary there. Then uncheck any you think may be causing issues. Or post them here is you need help.

Also, are you sure your antivirus and antispyware are up to date? And have you run scans with both?

Thanks for your reply.I have checked 'msconfig' and nothing has changed.I've also ensured my Norton Security is up to date.I've run ccleaner including the registry part of it.I've done a defrag with Auslogics.