dell dimension 9200

If you're looking at the unit straight on then there should be 2 tabs on the left side of the black front panel that line up on the computer itself.  Once you have the left side lined up in the notches then move it toward the right and it should snap back in securely.

can pics be posted on here,maybe with a picture of it might help

From reading the documenation, there's nothing that should be removable from the retention assembly. Might you have broken the piece off?

support.dell.com/.../parts.htm

hi,no it is,nt broke,I,ve looked at the manual and cant see where it goes but i,m sure it was off the blue sliding panel

hi thanks for reply but it,s not the front plastic panel,the thing i,m stuck on came from inside the pc,I think it was on the blue sliding plate that you have to pull back before the writer will come out,its a tiny bit of black plastic 3 inches long

thankyou for your help,maybe i will just leave it out then,thanks anyway for your advice

That black piece of plastic is used to secure the optical drive in place if you were using the system in a desktop configuration (laying on it's side).  However, this type of mounting require a different face plate and I don't believe Dell even made the different face plate for this type of mounting.  So they really should not have included that piece ont his system.  It will slide into the case at the very top of unit right above the blue lever you mentioned or it's also directly above the optical drive.  Or you don't necessarily need to put it back in since it's not needed.