hi Claire, the not starting up can be quite a number of things, from motherboard to grafix card! to memory!
it can even be faulty key board!
now the runing slow isue can be put down to not enufe memory, a computer depending on the operating system, needs so mutch memory to start the oparating system, then as you keep putting thing on the pc in takes moor memory, then you also need to keep your computer at peek leavel, by cleaning out tempory files, also by defragmentation of the files every so often!
not alot of people relise that when thay get a pc it may not have a lot of memory installed, and you may have to have some exstra put in!
hope this helps.
dangerous752
March 2009