Frequent error on Dell Dimension E521

lonestarfan

We have a dell dimension E521 which has been behaving very oddly the last 3 months.
It just stops working - I mean that its just a blank monitor when you switch it on but electricity is still there. The hard drive casing flashes 3, 4 all the time.
It did the same twice in a few years about 2 years ago and I took it to a shop and they wiped it clean and re-installed stuff for about £40 each time.
Then just before Christmas it did it with the 3,4 flashing and as I was busy I left it. Then for some bizarre reason it just started working again about 4 days later! At that point it said the time was 00.05 and the date was a date in 2003 - I can't remember the exact date and it said it needed updating. So I reset the date and time and went on windows update. It worked ok for about 4 weeks and then a week ago it stopped working again and the same thing happened a few days later where it started working but showed a 2003 date and time.
I would welcome anyones knowledge about what they think is happening here!
Many thanks.

macman

You need to replace the CMOS battery on the motherboard. Usually a CR2032 but not always. Costs a couple of quid.
This makes it possible to retain the date and time settings when the machine is shut down.
Edit: if by 'hard drive casing' you mean the 4 diagnostic lights. then nos. 3 and 4 flashing on the Dim E521 indicate a memory failure.
So suggest you remove each RAM chip in turn (if you have 2 or more) and retest to see if that clears the fault. One could be faulty or maybe just worked loose. if just one, you'll need to reseat it or replace it.
If you download the manual from the Dell support site you will find all the info you need.
BTW the two errors are not connected, CMOS batteries usually fail after 5 years or so.
http://support.dell.com/support/edocs/systems/dime521/