Intermittent net issues

Hi

Been having problems with my 4ish year old imac over the last month or so.

It is mainly effecting the internet performance and the occasional other random app.

3 months ago i moved house and change ISP to virgin fibre optic service. Safari+ firefox have both been having problems with what i though where very slow speeds, average browser page takes at least 45 seconds to open and quite often pages fail to open. My mac is running wireless and the airport symbol is showing full activity all the time.
At first I thought it was my ISP but tested net when i have problems on my wife's laptop which performs great. Online net speed checkers state my comp is receiving just over 20mb but a 6 mb file can take 6 hours to download.

The problem is only occasional but often enough to be a serious problem. Times like now it is performing fine.

My hard disk could be the problem but some recent housekeeping has had no positive effect. My HD (300gig) was filled to just over 250gig but now only just 233gig.

I have done a full back up and am thinking of doing a clean install to get rid of years of clutter(demo programs, unused stuff etc).

Anyone got any opinions weather my HD is the problem or could any environmental, hardware issues or even a resent dodgy download be causing my problems?

My mac is imac 2.4ghz intel core 2 duo, 2 gig ram, 300 gig HD(233 used), OS10.5.8.

With a 20 MB download speed, downloads should be fairly quick. However, a lot depends on the site you're downloading from. Not all servers are created equal.

I have a very fast connection (Verizon FiOS) and occasionally I run into a slow website that downloads like I was connected via dialup modem. Your hard drive is also approaching the point where everything is going to slow down. Time to swap it out for a larger faster drive.

Thanks for reply, this problem is not site dependant. One munite internet works, one munite it doesnt, the next it works very slowly.

I have been trying to get online all morning to check this site but gave up, now logging on with my wifes ancient pc laptop.

My drive may be slow compared to modern standards but I dont believe it is past it unless its worn out with a tech fault. I write/produce audio on mac and the intensive CPU apps involved for this are not affected by any issues. It is only the internet thaqt is a problem and only been happening over last month or 2.

When it slows down have you tried doing a traceroute in terminal to see exactly where the slowdown is happening?