I have an Inspiron 1525 with 4gb RAM and 285gb hard drive (158gb free). Processor is 2.17gHz, dual core. O/S Vista. Up until very recently, it's been running fine. But within the last week or two, it has gotten veerrryyy slow. The fan seems to be running more often (maybe it's my imagination), and the video is halting even for a simple game of Free Cell. I have ccleaner which I run regularly. I have also run two different spyware programs and Norton Utilities optimizer.
I just had to replace my desktop computer a few months ago. I certainly don't want to have to replace this one too. 
Hope someone has suggestions for me...