Woops - seem to have killed my laptop!

Question

 

Hi,

REcently posted the below problem.  Now have put it back as originally but now it won't even start up!!  Is there a way of rebooting it please??

 

Thanks

 

"Have recently put an extra 1GB memory to my Toshiba Satellite A100 (XP professional).  Opened the back, put in extra 1GB memory (from Legend) into the obvious place- and it appears to work - but exactly the same as before!!  Can't find anywhere where the new memory shows up, just the old 512 MB.  Is there something else to do like set it up somehow to recognise the new memory??  What test can be run to see if it is "