RAM is not the answer to speed up a system. A RAM will allow more programs to be opened at one time, less "caching" but that's about all.
What is in startup can be one issue. Spyware/Malware etc can be another, especially if some P2P program such as limewire is installed. Registry cleaners won't help and in many cases will cause problems rather than fixing them.
Dimension E510 with D925 CPU and Vista Home Premium 32 bit
Home Built PC with Q6600 CPU, 8GB RAM, HD4850 Video, HTO Striker 7.1 Audio Card - Windows 7 64 bit Professional
Sonar 8.5.1 ( Producer) DAW Software/Focusrite Saffire Pro 40 Recording Interface and Frontier Tranzport wireless controller.