Line speed probably isn't relevant here. It only matters for downloading and - to a certain extent - when browsing. Not for startup speed or speed of all other things when the PC is running.
So that leaves us with "My PC is slow."
That's generally caused by
(a) too much software running at the same time
(b) slow hardware (slow CPU, not enough RAM)
(d) a VERY fragmented and VERY full hard disk
(e) the hard disk being in PIO mode in stead of DMA (that's a setting in Device Manager)
It's up to you to find the cause and the remedy.
The easy way: find your recovery CD and bring the PC back to factory conditions. It's as fast then as it was when you bought it. Be sure to have a good backup of ALL your personal data, because everything you put on the machine yourself is gone, including all programs you installed way. It won't get faster than that. Only slower when you start installing programs and doing things.
The other way: step by step do-it-yourself. Find a cause and remove it.
I have a pc on XP and I have just done a dust clean on it but I dont think it has inproved it very much. I am with Virgin Meadia and the Line speed is 9666KBPS. Could anyone tell me what next I should do please.
Thanks T A Lefevre