Mittron :
I have 100% disk usage, only when downloading thing, otherwise its not even above 5%
What tool is telling you 100% disk usage? Do you mean your disk is FULL of stuff, or that it is reading or writing at 100% of its effective speed.
IF disk full is what you mean please say so and people will help you delete things with disk cleanup or install a larger disk.
IF disk running at 100% throughput is what you mean then can run
windows resource monitor (you can launch it out of task manager, or google it).
Post the make/model of your disk drive. Device manager will tell you if you don't know.
Post the disk queue length, MB/sec and IO response time from the resource monitor disk tab during the time you are seeing 100% disk utilization.