TAFFLAD,

Below are some links to help resolve your network installation issues. Most sites will not support IE6. You will need to update everything on this computer. If you choose to upgrade the OS on the E521 Dell only has Drivers for Vista 32/64 bit. 

How to reinstall Windows XP Professional SP3 on a Dell PC

Drivers and Downloads, Drivers Install Order and FAQs

Dell Networking and Wireless Support Center

Dell Dimension E521 Drivers,Downloads and Manuals

Wired internet connection for the home for Windows XP

•Microsoft Article: Internet firewalls can prevent browsing and file sharing (Windows XP

IE6=long past its End of Life, IE8=End of Life in April 2014, Windows XP=End of Life in April 2014... Theres not much time left, only 1 day but follow the Windows 10130 Insider Preview Upgrade Path to make the system a Windows 10 Pro Device for Free:

http://dellwindowsreinstallationguide.com/windows-xpvista-to-windows-10-free-upgrade/

Appreciate the end of life comments.

In order for me to upgrade I need to get it all working ... hence resorted to the OS reinstall disk and the DEll drivers disk.

I can't get on line on that PC to download anything yet.

The re-install was as per the link .......... when I installed the drivers Ethernet came to life .... but only on some sites.

Not working to the extent I can download any upgrades

OK .. just spent another several Hrs of fun.

One important thing I found it is IE related ONLYI

installed FireFox and that works fine .. allowed me to manually get SP3. & Kaspersky

Ran diagnostics it says HTTP, HTTPS & FTP is blocked .. and to change Firewall settings.

I disabled Windows Firewall as Kasperky installed (and working fine with Firefox)

Run diagnostics - same error

I found some IE and internet diagnostics on MS web site .. CAB files .... but XP does not know what to do with them, even if I unzip first it still does not know what to run files with.

I then found another IE fix entitled IEFIX .... ran all of that and it reports all is fine.

Need to get IE working as I can't get MS updates without it.

Forgot to add .. the test sites that IE fails on ... all ping OK from a cmd prompt .... and also connect fine from Firefox.

Use another PC to Download the 10130 .iso and 1586 .iso and create Bootable Media...

Alternatively if you wish to stick to XP which is ill-advised. Windows Update will likely just never work... There is an unofficial Service Pack 4....

http://www.softpedia.com/get/Others/Signatures-Updates/Windows-XP-SP4-Unofficial.shtml

Of course an "up to date Windows XP" is still 2 years unpatched...

If I understand this ... you suggest using W10 upgrade.

Will the Dimension E521   (Athlon 64x2dual)   be capable of running it ?

Just wondering if I'm better served getting it to W7

Although MS support for XP stopped at SP3

There is an unofficial SP4 aimed specifically for 32bit OS :

http://www.softpedia.com/get/Others/Signatures-Updates/Windows-XP-SP4-Unofficial.shtml

Anybody know is this is safe  to run on the E521

It gives IE8    which might fix my IE issues

If I understand this ... you suggest using W10 upgrade. Will the Dimension E521   (Athlon 64x2dual)   be capable of running it ? Just wondering if I'm better served getting it to W7

Yes it works. See here:

http://answers.microsoft.com/en-us/windows/forum/windows_10-hardware/dimension-e521-and-windows-10/1df33d26-2ca2-4d35-bd26-20b823fbec72?auth=1