Go to www.dyson.co.uk
click support look for user manuals download save and refer, or print out.
My daughters DC05 had the same problem very little suction even though she washed the filter and filter holder. I vacuumed both parts of the top filter and hey presto full suction back.
When you remove the dust box the motor filter housing has two thumb clips if the same as the DC05 pull them towards the duxt box slot and lif and that exposes the filter.
Retired vac spares market stall holder.
Bob, May 2010