CCleaner clean-up, checking System Restore space, Antivirus at Anti-Malware scans ay mga good advices. I recommend you do a quick or full scan with SuperAntiSpyware -
http://www.superantispyware.com and/or MalwareBytes' Antimalware -
http://www.malwarebytes.org/mbam.php (both are freeware).
Eto additional advice ko - use
WinDirStat - http://windirstat.info/ para malaman mo kung anong mga file at folder ang kumakain ng sobrang daming disk space
WinDirStat is a disk usage statistics viewer and cleanup tool for Microsoft Windows.
On start up, it reads the whole directory tree once and then presents it in three useful views:
• The directory list, which resembles the tree view of the Windows Explorer but is sorted by file/subtree size,
• The treemap, which shows the whole contents of the directory tree straight away,
• The extension list, which serves as a legend and shows statistics about the file types.
The treemap represents each file as a colored rectangle, the area of which is proportional to the file's size. The rectangles are arranged in such a way, that directories again make up rectangles, which contain all their files and subdirectories. So their area is proportional to the size of the subtrees. The color of a rectangle indicates the type of the file, as shown in the extension list. The cushion shading additionally brings out the directory structure.