if your Laptop  become very slow  you need to upgrade your laptop ,  hard drive in to solid state drive (SSD) and  upgrade RAM with more capacity. older laptops also very fast after upgrading,older laptop are upgrade-friendly and easy to upgrade in few common ways.

1.  Install RAM.

                       If your Laptops motherboard has  available RAM slot  it is easy to install  another RAM. If your laptops motherboard  slots are full it is possible to remove old one and replace with more capacity. some old laptops come with special memory panel located  on the bottom of the laptop and easy to install and  upgrade the RAM.

2. Upgrade  HDD to SSD.

                              If your  laptop come with  HDD  which is slower then SSD in this case also you may be able to upgrade it to SSD (solid state drive) which is more faster then  Hard drive , in this process you need to  open your laptop remove old hard drive and install solid state drive in it's place and install operating system.  some  new  model laptop motherboard have two slots  sata and m.2 sata or NVME . This types of laptop just install M.2 sata or NVME and install operating system in NVME or M.2 sata  and use hard disk for  storage purpose only.

3. Replace optical drive with SSD.

                    IF you want to  keep your laptops internal Hard drive and install solid state drive  in this case you need to  purchase DVD enclosure, by using DVD enclosure you may be able to replace  your optical disk drive to  solid state drive after that install  windows in solid state drive,and use internal HDD for storage purpose .